Just a few little tips I've had to use.

Disable 2FA on CLI.

su - apache -c "php /path/to/nextcloud/occ twofactorauth:disable username"

This will disable 2FA regardless of it it is enabled in the GUI.  You will need to enable 2FA by running the command again, but with enable instead.

Delete the undeleteables.

I had a situation where a user had ~30Gb of data in their nextcloud trash which they could not delete.  There were also files/directories in their active files that they also could not delete.  No errors in the logs, just unable to delete :(  The work around is to manually delete them from the server and then run the following command.

su - apache -c "php /path/to/nextcloud/occ files:scan <user>"

This removes invalid file references from the database.