One possible Server-Side solution for the plain URL trunking problem i have found and partly tested is to verify that the  /.well-known/caldav redirect (and carddav) is configured correctly. That Redirect on the webserver should catch any /.well-known/caldav /.well-known/carddav requests and redirect them to the right webdav path from the root of the Server. e.g: somecaldavserver.example.com/.well-known/caldav http 302 redirects to https https://somecaldavserver.example.com/nextcloud/remote.php/dav/ iOS needs secure https to work http will not work. The username will be attached to that url automatically. This Server Config would probably catch the URL trunking error during the update to iOS 15. At least it is fixed - in my test - if the user opens the calendar settings and simply accept them again with the trunked url. iOS will then autodiscover the correct url and stores it - somewhere - the displayed url stays short - but it works! No need to fill out the whole path again. iOS will find the correct long path by itself (with the redirect) As of lack of time i couldn´t setup an iOS14 test device just to update it to ios 15 to check if the server side fix also works on that trunking without the user to open and close the settings. I could test and verify in on my nextcloud Server - on SOGo i don´t have access to the misconfigured apache config to run a test. Maybe anyone else could verify if this thing works for them. Bonus If you add _caldavs._tcp SRV  0 1 443 somecaldavserver.example.com _carddavs._tcp SRV  0 1 443 somecaldavserver.example.com to your DNS Entrys your users even don´t know the name of your somecaldavserver and could just enter example.com in the calendar and contacts server field. Instead of somecaldavserver.example.com best regards, Elmar