I would go with Jellyfin as a server and Mopidy client as outputs. Like an rpi with an audio hat or class d amp hat. Planning to add Snapcast to the mix for multiroom audio but didn’t find the time yet.

mp3

Using a GitHub repository wiki is a low effort / zero cost option. https://docs.github.com/en/communities/documenting-your-project-with-wikis (Clearly not as charming as something self hosted though)