Bigfoot

I use SyncThing to monitor and copy my photos to an (encrypted, offsite) drive.

I am in a similar boat. Since you have Tidal might want to look into Tidal-dl to “backup” the things you especially like in high quality.

Tidal is actually not too bad, and it pays artists more than other services (not a lot, just more) but I do expect it to go downhill/away eventually so I make a habit of downloading what I can and supporting the artist directly in other ways.

I don’t know why nobody has mentioned Anytype, which is excellent and just recently added collaboration.

https://doc.anytype.io/anytype-docs/intro/collaboration