if you just care about listening to mp3s across all your devices then navidrome is a good choice imo. because it supports the subsonic api, there are a lot of good players for it like feishin for desktop and dsub for android and a built-in web player.

as for sharing music, soulseek is already pretty established for this. it basically allows you to search for and download music from anyone on the network (remember to share some yourself, it's good manners).

the setup i use is basically a server (all these programs are pretty light, so you can probably run it on a spare laptop or even a raspberry pi) with:

• slskd as a constantly running soulseek client, allowing me to download music to my server through the built-in web interface
• beets, to automatically tag any music i download, based on information from musicbrainz. you can configure slskd to run commands when downloads finish, so i just run beets to import any new music
• navidrome as the server to actually serve all the music

the only real gripe i have with this setup is that while navidrome has support for multiple users, so i can easily allow friends to listen to my music collection, slskd doesn't have that (yet, it's planned), so if someone wants music added to the server they have to ask me to download it through slskd, which is a bit tedious. it works really well if you're the only person using it though