I just wanted to say thank you for your work. I’ve used m4b-tool and some other projects that use it as a dependency and I am glad to be reminded of tone. It was just getting started last I looked at the project.
I'm also sometimes working on `Tone Audio Player` (https://github.com/sandreas/ToneAudioPlayer), which is planned as cross platform iPod Nano inspired app, that is able to stream and download from different services (Navidrome, Audiobookshelf, Jellyfin, Kodi, etc.). But this project has just started and will not really progress until I have more time.
If you are interested, take a look at AvaloniaUI (https://avaloniaui.net/), a really nice cross platform (incl. WASM) UI Toolkit for C#.