I've been self-hosting Nextcloud for calendar and file sharing for a few years now. I use DAVx5 on my Android device and my wife's iphone syncs out of the box.

I've been self-hosting Nextcloud for calendar and file sharing for a few years now. I use DAVx5 on my Android device and my wife's iphone syncs out of the box. It's been a very solid solution for us and isn't that difficult to get up and running.