"config" directory not writable after upgrade from 13 to 14.0.4

Hi, after manually upgrading from 13.x to 14.04. I can only start NC when “config_is_read_only” is set to true in config.php. Otherwise I get the message that the “config” directory is not writable, which is not true:
User and group of both config directory and config.php is “apache” (httpd is running under this account) and permissions are 750 for the dir and 640 for the files. I even can edit the config.php under the apache account with the following command:

sudo -u apache vi config/config.php

Neither in syslog nor apache log nor nextcloud.log is a single entry regarding this issue when starting apache and trying to open the nextcloud site.

Thanks in advance for every hint! :slight_smile: