I find myself using this all the time. Short press the speed button to change speeds. Long-press for finer control. Treats audio files like video files too, when it comes to seeking within a file, unlike VLC. Also shows the video image when quickly seeking through a file visially. MPV is a very nice app.
Hopefully someday the necessary work will be done so that it can be included in F-Droid, since the youtube-dl executable is downloaded from the developer’s server.
Note FWIW to any who care about their app consumption pipelines:
VLC is developed on a self-hosted gitlab, which has a free license IIUC; however, mpv-android and youtube-dl are on microsoft github, which is a proprietary non-free net “service”.