If you're ready to self-host, you can always install Nextcloud and use its calendar app.
These are in no way the only options, but I've found these to be good myself.
Just to emphasise, you don't need to self-host to use Nextcloud.
You can sign up for Nextcloud just like signing up for email.
@jez @switchingsocial @Stoori @PhilthePill can confirm, Nextcloud calendar is the shit. The web client is decent but nothing too exciting, the fact that every and any client that understands CalDAV or ICS can communicate with it is absolutely amazing.
And that's before you do the same with your contacts.
Signs & Codes is a private Mastodon instance built around a community of friends.