29
Music player recommendations
(feddit.uk)
F-Droid is an installable catalogue of FOSS (Free and Open Source Software) applications for the Android platform. The client makes it easy to browse, install, and keep track of updates on your device.
Matrix space | forum | IRC
I've been using VLC for folder based play of audio files. The UI is not ideal but it works well and the other apps I've tried didn't work out for various reasons. Unfortunately the Android Auto version of the UI doesn't have access to the folder browsing feature.
No idea if VLC has lyrics support for audio-only files.