Fastmail has great calendar (CalDAV), contacts (whatever the open protocol for this is) support in addition to their e-mail. I migrated from Google Calendar & friends several years ago and have had no issues.

Another vote for this option being a viable, and dare I say good, one. In addition to the CalDAV, contacts and email you can use davx5[0] on Android to help with syncing to your (root-not-required) Android device.

This setup has worked well for me for a little under a year at this point.

[0]: https://www.davx5.com/

I use Nextcloud. Not very happy with it, though.

Use Baikal or radicale. I’ve been running baikal in a docker container for a couple of years.

I personally sync calendars with my Android phone using Nextcloud and Davx5.

I'm using Etesync for half a year and it's working great for me.

I use mailbox.org and they have CalDAV.