the tutorial followed is incorrect at the point where they change config.php they use a different directory as in there example above where they change permissoins.
this might be confusing to a novice user.
the datadirectory in the tutorial should be set to
‘datadirectory’ => ‘/media/linuxbabe/b43e4eea-9796-4ac6-9c48-2bcaa46353731/nextcloud-data/’