Why not tus-flutter-client?
tus-flutter-client does not seem to be maintained anymore. It is not necessary to call iOS and Android separately. The tus protocol can be implemented with pure dart http.
If you are able to complete background tus uploads with tus_client I would very much like to see how you do that. Otherwise, I don't think you'd be able to do so, at least on iOS, with a dart implementation.
Why tus_client? Use pure dart to implement tus flutter client, which is very useful for flutter developers. https://github.com/jjmutumi/tus_client
Why not tus-flutter-client? tus-flutter-client does not seem to be maintained anymore. It is not necessary to call iOS and Android separately. The tus protocol can be implemented with pure dart http.