If you connect your calendar via CalDAV, locations will link to maps on iOS, but then you are no longer able to accept any invitation, see other bug submitted by me

It seems that iOS enables this feature only when the server provides EAS protocol version 16.x. Currently Sogo offers EAS14.1.

Thanks a lot for the explanation, a workaround is:
Connect via CalDAV/IMAP on iOS with SoGO, then location with maps works properly.

hoping for EAS16 to be supported. Is there any plan/timeline for that?

The mentioned workaround by installing the CalDAV calendar on an iPhone unfortunately has a flaw:

If you receive an invitation (in email), iOS will NOT show this invitation in the calendar inbox, but only pencil that event into your calendar. You would have to go to the specific date, open that greyish, pencilled-in event in calendar and then confirm with "Accept".

If you look only into the invitation email, open the .ics file, you cannot accept the invitation properly, such that the server will notice it.
Don't know if SoGO can change something about this, it seems that iOS does not properly process the invitation emails from SoGo received for a CalDAV calendar....

With EAS, invitations properly flow into the calendar inbox, BUT with the above mentioned limitation, that calendar event locations lose their link to Apple Maps.

So, praying for SoGO to support EAS16!!! That would solve all limitations.