After a couple years of rewriting SyncKit to combine ideas from IceCream and focusing only on RealmSwift (given that CoreData has SwiftData as its successor), I've achieved production stability in my fork named BigSyncKit: https://github.com/lake-of-fire/BigSyncKit

I recommend that this project deprecates itself in favor of this more scalable approach

I haven't caught up on docs and testing but have been successfully using this in production in my apps, with hundreds of thousands of records

I can add more info if there is interest