@sad_electronics Shared as in to share with other people?

I use #Etesync (has calendar, tasks and contacts). You can selfhost for free or don't, like I do, €24/year; Belgian I think.
Support is good. Not a lot of problems, but also very little feature development. Integrates with a lot of things. Works nicely with Thunderbird.

But I don't know how sharing works. I think read only wasn't a real problem though. But never used it.