I want to create a typescript/JS/blazor example, basically something entirely web-based and run in the browser (no online storage).
I load a file system from a device using web-serial, then decode that binary blob to a FAT / SpiffFS/LittleFS file system and now wish to have a file browser using the syncfusion javascript tools.

Could someone give me pointers on how to handle an in-memory file system. For the sake of argument you could instead just fetch (using ajax) and extract a zip (to an in-memory store) and pretend that was my file system. Then use the file manager component to view that zip data including image preview like your sample project shows.

I don't really care if I get to do this in blazor (wasm/client side) or just pure JS/typescript.
I've not started on the interface, although it's an extension of this embedded device reading site for programming and reading flash partitions from Espressif ESP32 based microcontrollers: https://github.com/tyeth/read-partitions-esptool-js/tree/readCurrentPartitions