Nextcloud app auto upload issue after server migration of old data to new server hardware

Dear Nextclouders,

recently I migrated my Nextcloud data to a more powerful server which resulted in different Nextcloud server address. I followed this geat LEMP stack installation tutorial [1] and data restore guide [2].

Nextcloud version: 13.0.5 (same before and after new installation)

All clients of the users are able to flawlessly sync via CalDAV and CardDAV again. iOS devices simply required a modified Nextcloud server address. In Android devices I managed to revert to nomal operation when I created a new account in DavDroid with same user credentials as before. In DavDroid I deactivated all address books and calendars of the old account. The new account was able to find all address books and calendars as it used to be.
The message after pressing ‘delete account’ in DavDroid scares me a bit since it states that all address books and calendars will be deleted from the device but not from the server. Is it safe to proceed the deletion of the old Nextcloud accound in DavDroid since the newly created account pulls all data from the server back in place again?

In the Nextcloud App of iOS I created a new account and deleted the old one. Auto upload of photos/ videos works now with newly taken shots. In Android devices I created a new account as well and under auto upload I did the adjustments (remote folder and upload into year/ months folders). Unfortunately, the Andriod app still trys to upload with the old account despite the new account is selected in first place as shown on top of the Nextcloud app menue. What needs to be done in order to activate the Nextcloud app with the new account without messing around with files already uploaded? It smells that the loop is closed to the first question above about DavDroid account deletion…
Simply changing the server path in Android Nextcloud app is not possible from what I read. Is that correct?

Thanks a lot in advance.

[1] [DE] Tutorial: Nextcloud auf Ubuntu Server mit nginx, MariaDB, PHP, Let’s Encrypt, Redis und Fail2ban

Would anybody please jump in to shed light into this?

What is the recommended way to reconnect clients with installed Nextcloud app / DAVDroid combination after a server migration/ restore?

I noticed that e.g. the appointments put into the Android phones calendar during the offline phase of the Nextcloud server disappeared after reconnect via CalDav… I want to prevent this behavior with all of the photos taken during this phase.