I use the tchapi docker image for the caldav server (die to the LDAP support for the user Auth) and davx5 for the android integration.

In Desktop thunderbird already have a native integration and with iPhone is also working fine.

No problems so far in almost a year, they work reliable and smooth. The only point I somehow miss is the lack of push notifications from the server to the devices, but it is not a deal breaker from me

Another one selfhosting contacts, calendar, notes and so on with that non-interoperable protocol.

And for the shake of honesty I need to say that while doable it is true that the situation could be highly improved with a lot of non standard stuff that private apps are implementing outside of the standard compliance