@longshots mentioned this proprierary music player, the thread was locked I just want to warn.

There is a ton of music players and that one wants network access and dynamic code loading, use something else.

I currently use Anrimians Musicplayer which is pretty nice. It has folder and playlist support.

Playlists are saved as .m3u files in /Music.

In the past I tried to have my music in a custom folder but that was a pain. I have all the music files in /Music too and sync the entire folder with Syncthing.

The .m3u files reference the music files relatively (like "this folder but in subfolder /classical"), so as they are in the same folder, you can sync it to your laptop to any location. On Linux I use Gapless, a modern and minimalist player.

I can edit and use my playlist files without issues (as long as syncthing syncs them before I edit them).

    DeletedUser33 I think Syncthing is unreplaceable currently.

    Just wanted to recommend the music player and yall can name some that also work like this!

        missing-root

        Oh my bad, I misread that you wanted and alternative to Syncthing for music syncing.
        For listening to music on my smartphone I always used VLC which has playlist and folder support.
        It also does not have invasive permissions and works without network permissions if you disable it.

          I still use ArmAmp from time to time 😎😎😎 Hella ugly UI, great UX, lots of customizability and equalizing options. Works nicely with WebDAV servers and SMB and possibly still with GDrive and Dropbox, never tested that.

          I would just recommend Auxio to others.

            missing-root The website states it automatically updates lists imported from m3u files if those playlist files change, so it's not completely manual. I didn't know it couldn't write to them, though.

                I'm not entirely sure what you're looking for, so this might not be a perfect fit, but I've had good experiences with Poweramp and Musicolet.
                If you are seeking a music player with the direct capability to synchronize folders, you may ignore this part:

                Musicolet has a more "cluttered" user interface but has definitely more options for editing the music library.
                Poweramp, on the other hand, seems to have a better audio chain and a cleaner UI. I can't say whether the audio chain actually produces different audio quality, so you'll have to test it yourself. I bought both of them, and they're totally worth it.

                I'm using Navidrome + Ultrasonic or Tempo. Yes this could(!) be an online "Spotify" replacement, and I'm using it like this, but you can run Navidrome locally at home and sync to Ultrasonic/Tempo for offline play over WiFi. You can remove network permission from Ultrasonic/Tempo after syncing as well, it will work just fine.

                • Tempo is a nicer app and has better offline support
                • Ultrasonic is more stable and works a lot better for streaming (which you don't care about)