I second nextcloud, have been running it for years and have only had an update issue once, I rolled back and repeated the update without issue.

I also run collabra and whiteboard to have a full Google replacement

Seconding radicale, I’ve been using it for over a year and it’s been rock solid. I can’t say the same about NextCloud, it seemed to break every update and was slow as hell. I moved to SyncThing and never looked back.

Thanks!