Comment by port11
Calendars are a tough issue, I'm not sure what I'd recommend. My partner's on Outlook so many of the OSS options won't work for sharing our calendars.
I can move her entirely to the family server, but even I'm confused. There's too many Calendar servers with different features, and all with a generally terrible UI. Once I finally settle for one of the server options, I'd have to get her using whatever calendar agent is good on Android, but that's another 20+ options to look at.
Sometimes the bazaar is quite confusing and overwhelming.