I just did a hunt for some recent info on libre.fm and found a blog with updates…
https://librefm.wordpress.com/2024/10/06/bunch-of-updates-to-libre-fm-this-week-2024-10-06/
looks like the reboot of libre.fm is located at https://github.com/foocorp/hacienda but is still very in the starting stages.
My brain went to the caldav server and was lost.
https://radicale.org/v3.html