you can create a context with

import android.app.Application
 val context = Application()

I tried this approach below, and I have this bug here when compile to Desktop using Firebase.

Inside commonMain, App.kt:

@OptIn(ExperimentalResourceApi::class)
@Composable
fun App() {
 val context = Application()
 Firebase.initialize(context)
 MaterialTheme {
 var showContent by remember { mutableStateOf(false) }
 val greeting = remember { Greeting().greet() }
 Column(Modifier.fillMaxWidth(), horizontalAlignment = Alignment.CenterHorizontally) { ...

Inside dektopMain:

fun main() = application {
 Window(onCloseRequest = ::exitApplication, title = "FourWaysProject") {
 App()
 }
}

Error:

Exception in thread "main" java.lang.NoClassDefFoundError: com/google/android/gms/common/R$string
at com.google.android.gms.common.internal.StringResourceValueReader.(com.google.android.gms:play-services-basement@@18.0.0:3)
at com.google.firebase.FirebaseOptions.fromResource(FirebaseOptions.java:156)
at com.google.firebase.FirebaseApp.initializeApp(FirebaseApp.java:245)
at dev.gitlive.firebase.FirebaseKt.initialize(firebase.kt:24)
at ComposableSingletons$MainKt$lambda-11ドル.invoke(main.kt:12)
at ComposableSingletons$MainKt$lambda-11ドル.invoke(main.kt:10)
at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:117)
at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:35)
at androidx.compose.ui.awt.ComposeWindow$setContent5ドル.invoke(ComposeWindow.desktop.kt:161)
at androidx.compose.ui.awt.ComposeWindow$setContent5ドル.invoke(ComposeWindow.desktop.kt:160)
at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:108)
at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:35)
at androidx.compose.ui.awt.ComposeWindowDelegate.WindowContentLayout(ComposeWindowDelegate.desktop.kt:168)
at androidx.compose.ui.awt.ComposeWindowDelegate.access$WindowContentLayout(ComposeWindowDelegate.desktop.kt:43)
at androidx.compose.ui.awt.ComposeWindowDelegate$setContent3ドル1ドル.invoke(ComposeWindowDelegate.desktop.kt:156)
at androidx.compose.ui.awt.ComposeWindowDelegate$setContent3ドル1ドル.invoke(ComposeWindowDelegate.desktop.kt:155)
at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:108)
at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:35)
at androidx.compose.runtime.CompositionLocalKt.CompositionLocalProvider(CompositionLocal.kt:228)
at androidx.compose.ui.awt.ComposeWindowDelegate$setContent3ドル.invoke(ComposeWindowDelegate.desktop.kt:152)
at androidx.compose.ui.awt.ComposeWindowDelegate$setContent3ドル.invoke(ComposeWindowDelegate.desktop.kt:151)
at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:108)
at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:35)
at androidx.compose.runtime.CompositionLocalKt.CompositionLocalProvider(CompositionLocal.kt:228)
at androidx.compose.ui.ComposeScene$setContent5ドル.invoke(ComposeScene.skiko.kt:474)
at androidx.compose.ui.ComposeScene$setContent5ドル.invoke(ComposeScene.skiko.kt:473)
at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:108)
at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:35)
at androidx.compose.runtime.CompositionLocalKt.CompositionLocalProvider(CompositionLocal.kt:228)
at androidx.compose.ui.platform.CompositionLocalsKt.ProvideCommonCompositionLocals(CompositionLocals.kt:195)
at androidx.compose.ui.platform.Wrapper_skikoKt$setContent2ドル1ドル.invoke(Wrapper.skiko.kt:47)
at androidx.compose.ui.platform.Wrapper_skikoKt$setContent2ドル1ドル.invoke(Wrapper.skiko.kt:46)
at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:108)
at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:35)
at androidx.compose.runtime.CompositionLocalKt.CompositionLocalProvider(CompositionLocal.kt:228)
at androidx.compose.runtime.CompositionLocalKt.CompositionLocalProvider(CompositionLocal.kt:248)
at androidx.compose.ui.platform.Wrapper_skikoKt.provide(Wrapper.skiko.kt:61)
at androidx.compose.ui.platform.Wrapper_skikoKt.access$provide(Wrapper.skiko.kt:1)
at androidx.compose.ui.platform.Wrapper_skikoKt$setContent2ドル.invoke(Wrapper.skiko.kt:46)
at androidx.compose.ui.platform.Wrapper_skikoKt$setContent2ドル.invoke(Wrapper.skiko.kt:45)
at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:108)
at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:35)
at androidx.compose.runtime.ActualJvm_jvmKt.invokeComposable(ActualJvm.jvm.kt:39)
at androidx.compose.runtime.ComposerImpl.doCompose(Composer.kt:3341)
at androidx.compose.runtime.ComposerImpl.composeContent$runtime(Composer.kt:3274)
at androidx.compose.runtime.CompositionImpl.composeContent(Composition.kt:588)
at androidx.compose.runtime.Recomposer.composeInitial$runtime(Recomposer.kt:1013)
at androidx.compose.runtime.CompositionImpl.setContent(Composition.kt:520)
at androidx.compose.ui.platform.Wrapper_skikoKt.setContent(Wrapper.skiko.kt:45)
at androidx.compose.ui.ComposeScene.setContent$ui(ComposeScene.skiko.kt:470)
at androidx.compose.ui.ComposeScene.setContent$ui$default(ComposeScene.skiko.kt:448)
at androidx.compose.ui.awt.ComposeBridge$setContent3ドル1ドル.invoke(ComposeBridge.desktop.kt:306)
at androidx.compose.ui.awt.ComposeBridge$setContent3ドル1ドル.invoke(ComposeBridge.desktop.kt:305)
at androidx.compose.ui.awt.ComposeBridge.catchExceptions(ComposeBridge.desktop.kt:150)
at androidx.compose.ui.awt.ComposeBridge.access$catchExceptions(ComposeBridge.desktop.kt:64)
at androidx.compose.ui.awt.ComposeBridge$setContent3ドル.invoke(ComposeBridge.desktop.kt:305)
at androidx.compose.ui.awt.ComposeBridge$setContent3ドル.invoke(ComposeBridge.desktop.kt:304)
at androidx.compose.ui.awt.ComposeBridge.initContent(ComposeBridge.desktop.kt:320)
at androidx.compose.ui.awt.WindowComposeBridge$component1ドル.addNotify(WindowComposeBridge.desktop.kt:50)
at java.desktop/java.awt.Container.addNotify(Container.java:2804)
at java.desktop/javax.swing.JComponent.addNotify(JComponent.java:4839)
at androidx.compose.ui.awt.ComposeWindowDelegate$_pane1ドル.addNotify(ComposeWindowDelegate.desktop.kt:87)
at java.desktop/java.awt.Container.addNotify(Container.java:2804)
at java.desktop/javax.swing.JComponent.addNotify(JComponent.java:4839)
at java.desktop/java.awt.Container.addNotify(Container.java:2804)
at java.desktop/javax.swing.JComponent.addNotify(JComponent.java:4839)
at java.desktop/java.awt.Container.addNotify(Container.java:2804)
at java.desktop/javax.swing.JComponent.addNotify(JComponent.java:4839)
at java.desktop/javax.swing.JRootPane.addNotify(JRootPane.java:729)
at java.desktop/java.awt.Container.addNotify(Container.java:2804)
at java.desktop/java.awt.Window.addNotify(Window.java:791)
at java.desktop/java.awt.Frame.addNotify(Frame.java:495)
at java.desktop/java.awt.Window.pack(Window.java:829)
at androidx.compose.ui.util.Windows_desktopKt.setSizeImpl-6HolHcs(Windows.desktop.kt:116)
at androidx.compose.ui.util.Windows_desktopKt.setSizeSafely-hQcJfNw(Windows.desktop.kt:55)
at androidx.compose.ui.window.Window_desktopKt$Window5ドル.invoke(Window.desktop.kt:237)
at androidx.compose.ui.window.Window_desktopKt$Window5ドル.invoke(Window.desktop.kt:174)
at androidx.compose.ui.window.Window_desktopKt$Window12ドル1ドル.invoke(Window.desktop.kt:425)
at androidx.compose.ui.window.Window_desktopKt$Window12ドル1ドル.invoke(Window.desktop.kt:418)
at androidx.compose.ui.window.AwtWindow_desktopKt$AwtWindow3ドル.invoke(AwtWindow.desktop.kt:78)
at androidx.compose.ui.window.AwtWindow_desktopKt$AwtWindow3ドル.invoke(AwtWindow.desktop.kt:76)
at androidx.compose.ui.util.UpdateEffect_desktopKt$UpdateEffect2ドル$performUpdate1ドル.invoke(UpdateEffect.desktop.kt:59)
at androidx.compose.ui.util.UpdateEffect_desktopKt$UpdateEffect2ドル$performUpdate1ドル.invoke(UpdateEffect.desktop.kt:55)
at androidx.compose.runtime.snapshots.Snapshot$Companion.observe(Snapshot.kt:2300)
at androidx.compose.runtime.snapshots.SnapshotStateObserver$ObservedScopeMap.observe(SnapshotStateObserver.kt:471)
at androidx.compose.runtime.snapshots.SnapshotStateObserver.observeReads(SnapshotStateObserver.kt:234)
at androidx.compose.ui.util.UpdateEffect_desktopKt$UpdateEffect2ドル.invoke$performUpdate(UpdateEffect.desktop.kt:55)
at androidx.compose.ui.util.UpdateEffect_desktopKt$UpdateEffect2ドル.invoke(UpdateEffect.desktop.kt:64)
at androidx.compose.ui.util.UpdateEffect_desktopKt$UpdateEffect2ドル.invoke(UpdateEffect.desktop.kt:47)
at androidx.compose.runtime.DisposableEffectImpl.onRemembered(Effects.kt:81)
at androidx.compose.runtime.CompositionImpl$RememberEventDispatcher.dispatchRememberObservers(Composition.kt:1137)
at androidx.compose.runtime.CompositionImpl.applyChangesInLocked(Composition.kt:828)
at androidx.compose.runtime.CompositionImpl.applyChanges(Composition.kt:849)
at androidx.compose.runtime.Recomposer.composeInitial$runtime(Recomposer.kt:1041)
at androidx.compose.runtime.CompositionImpl.setContent(Composition.kt:520)
at androidx.compose.ui.window.Application_desktopKt$awaitApplication2ドル1ドル2ドル.invokeSuspend(Application.desktop.kt:219)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:108)
at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:318)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:771)
at java.desktop/java.awt.EventQueue4ドル.run(EventQueue.java:722)
at java.desktop/java.awt.EventQueue4ドル.run(EventQueue.java:716)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:741)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Caused by: java.lang.ClassNotFoundException: com.google.android.gms.common.R$string
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520)
... 111 more

Task :composeApp:run FAILED

FAILURE: Build failed with an exception.

• What went wrong:
  Execution failed for task ':composeApp:run'.

Process 'command 'C:\Program Files\Java\jdk-17\bin\java.exe'' finished with non-zero exit value 1

• Try:

Run with --stacktrace option to get the stack trace.
Run with --info or --debug option to get more log output.
Run with --scan to get full insights.

• Get more help at https://help.gradle.org

BUILD FAILED in 30s
5 actionable tasks: 4 executed, 1 up-to-date
PS D:\project> ./gradlew :composeApp:run
Type-safe project accessors is an incubating feature.

Task :composeApp:run

Please read https://github.com/GitLiveApp/firebase-java-sdk/blob/master/README.md#initializing-the-sdk

For me it worked this way:

Inside commonMain, App.kt:

fun App() {
 val context = Application().applicationContext
 FirebasePlatform.initializeFirebasePlatform(object : FirebasePlatform() {
 val storage = mutableMapOf<String, String>()
 override fun store(key : String, value : String) = storage.set(key, value)
 override fun retrieve(key : String) = storage[key]
 override fun clear(key : String) { storage.remove(key) }
 override fun log(msg : String) = println(msg)
 })
 val options : FirebaseOptions = FirebaseOptions.Builder()
 .setProjectId("your-projeid")
 .setApiKey("your-apikey")
 .setApplicationId("your-appId")
 .build()
 Firebase.initialize(context, options)
 MaterialTheme{
 //your-compose-content
 }
}

Inside dektopMain:
fun main() = application { Window(onCloseRequest = ::exitApplication, title = "FourWaysProject") { App() } }

But now I have another problem, when I log the user into "FirebaseAuth", and it gives an error in "coroutines".
This happens whenever I run it on desktop, on Android it works normally

Inside commonMain, App.kt:

val auth = FirebaseAuth.getInstance()
 auth.signInWithEmailAndPassword("teste@email.teste", "123456")

Error:
Exception in thread "OkHttp https://securetoken.googleapis.com/..." java.lang.IllegalStateException: Module with the Main dispatcher is missing. Add dependency providing the Main dispatcher, e.g. 'kotlinx-coroutines-android' and ensure it has the same version as 'kotlinx-coroutines-core'
at kotlinx.coroutines.internal.MainDispatchersKt.throwMissingMainDispatcherException(MainDispatchers.kt:81)
at kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.missing(MainDispatchers.kt:112)
at kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.isDispatchNeeded(MainDispatchers.kt:96)
at kotlinx.coroutines.internal.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:319)
at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:30)
at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable$default(Cancellable.kt:25)
at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:110)
at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:126)
at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch(Builders.common.kt:56)
at kotlinx.coroutines.BuildersKt.launch(Unknown Source)
at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch$default(Builders.common.kt:47)
at kotlinx.coroutines.BuildersKt.launch$default(Unknown Source)
at com.google.firebase.auth.FirebaseAuth.setUser(FirebaseAuth.kt:147)
at com.google.firebase.auth.FirebaseAuth.access$setUser(FirebaseAuth.kt:104)
at com.google.firebase.auth.FirebaseAuth$enqueueRefreshTokenCall1ドル.onResponse(FirebaseAuth.kt:332)
at okhttp3.RealCall$AsyncCall.execute(RealCall.java:203)
at okhttp3.internal.NamedRunnable.run(NamedRunnable.java:32)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
at java.base/java.lang.Thread.run(Thread.java:840)
Suppressed: kotlinx.coroutines.internal.DiagnosticCoroutineContextException: [StandaloneCoroutine{Cancelling}@1dec9e31, Dispatchers.Main[missing]]