If you run your own Plex server, Plexamp is a fantastic music player. You do need to have a Plex Pass subscription or lifetime pass though.
Aegis and Authenticator Pro are good choices for TOTP two-factor authentication. Both are free and open-source. Authenticator Pro supports WearOS which I like since I can get my 2FA codes on my watch. Aegis is very principled and don't allow any non-open-source code in their project. I really respect that, but it does mean that they don't support watches, as supporting WearOS requires using a closed-source SDK from Google.