Hi together,
i made an upgrade on my nextcloud system. The upgrade was sucessfull without problems. The cloud runs after the upgrade. But then… i made an reboot…
Since reboot the webinterface is just a white page. I check the logs from the webserver and could find a lot of entries like this:
FastCGI sent in stderr: "PHP message: PHP Fatal error: Interface 'Doctrine\DBAL\Driver' not found in /var/www/html/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php on line 22"
I tried to make maintainance:repair but have the same error:
PHP Fatal error: Interface 'Doctrine\DBAL\Driver' not found in /var/www/html/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php on line 22
To my system:
Raspberry PI 3
Debian Buster
PHP 7.3
Maria DB
NGINX Webserver
Nextcloud Old: 17.0.x
Nextcloud new: 18.0.4
I have really no idea where the issue could be. I hope you can help 
Regards
Pak