The problem is that you have renamed your datadirectory to something other than data (which is fine in general) but then left it in the installation folder for the Nextcloud Server application (which is not fine).
You have a couple options:
Option One (Move your datadirectory)
This is the best one long-term and will never have to be done again, but it’ll require the most upfront work.
You could move your .xxxxx.data directory, but that will require a bit more work since your particular problem means you can’t leave a symbolic link in place (so you’ll need to follow the first approach which entails adjusting your database oc_storage table too):
Option Two (Temporarily move your datadirectory)
This will require less work, but will also need to be done every time you update/upgrade. It also still needs to be performed carefully to make sure.
Put your NC Server into maintenance mode: occ maintenance mode --on
Temporarily rename the .xxxxx.data to folder simply data
Temporarily change your datadirectory value in your config.php to match the rename by changing it also simply to data
Run the Updater (from the command-line) and say “no” when it offers to turn off maintenance mode
Rename your data folder back to .xxxxx.data
Restore your prior datadirectory value in your config.php (to point back at your restored-in-name .xxxxx.data folder)
Turn off maintenance mode: occ maintenance mode --off