This one: https://download.nextcloud.com/server/installer/setup-nextcloud.php for installing NC on shared hosts.
While installing i told the installer “/var/www/html/nc-data/” should be the NC data folder. The folder “nc-data” was created but empty, because the installer created the standard folder “data” with the .htaccess file in it, as well the path in config.php was “…/data” instead of “…/nc-data”.
The empty file .ocdata was missing - is it not necessarry anymore in NC 14?
Edit:
It comes from a php version mismatch and incorrect Apache settings -> solved.