To use StreamingAssets folder of Unity.
StreamingAssets is compressed jar file in Android builds, so default FileSystem cannot properly access to it.
BakingSheet includes StreamingAssetsFileSystem to support this. It is required to install BetterStreamingAssets package to use.
To install BetterStreamingAssets, install git package via Add package from git url....
https://github.com/cathei/BetterStreamingAssets-Package.git
You can also use OpenUPM.
openupm add com.cathei.betterstreamingassets
Or install from original BetterStreamingAssets repository.
Below is example of using StreamingAssetsFileSystem with JsonSheetConverter at runtime. Keep in mind that path is relative from Assets/StreamingAssets.
// create json converter from path
var jsonConverter = new JsonSheetConverter("Relative/Json/Path", new StreamingAssetsFileSystem());
// load from json
await sheetContainer.Bake(jsonConverter);