I have SOGo deployed, and want to use Nextcloud Contact, Calendar & Mail apps as frontent to my email system.
Can I setup usage my SOGo CardDAV/CalDAV server instead of Integrated SabreDAV?
At last resort, can I use my LDAP server as addressbook for mail app?
I’ll suggest you post directly on the github tracker for the mail app.
Concerning the contacts app, you want to change the server used by the app?
Yes. I want use Nextcloud Calendar App with existing CardDAV server (SOGo) instead of integrated into Nextcloud server
Then I’ll suggest you edit the app source code and change your web dav server. You’ll need developer knowledge and compilation environment.