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
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