I am using this NC12 compatible version of the user_sql plugin:
However it seems the AJAX saving/verifying of the sql database configuration seems to be not working for me as I get an 500 server error on the /ajax/settings.php, see:
Anyone got an idea what could be causing this? I suspect it to be an issue with the shared host I am trying to run this on (OVH), but I can’t quite nail it down as there is no error message in the OVH provided error log either.
I guess the best would be to just disable the entire AJAX functionality as it is not really needed I guess.
Any ideas or suggestions?
I am already thinking about manually adding the needed settings into my Postgres database Nextcloud runs on 
Interesting reply with an actual error message (my shared host doesn’t give one):
Call to a member function getValue() on null at /var/www/nextcloud/lib/private/DB/ConnectionFactory.php#81
Undefined variable: systemConfig at /var/www/nextcloud/lib/private/DB/ConnectionFactory.php#80
Argument 1 passed to OC\DB\ConnectionFactory::__construct() must be an instance of OC\SystemConfig, none given, called in /var/www/nextcloud/apps/user_sql/ajax/settings.php on line 162 and defined at /var/www/nextcloud/lib/private/DB/ConnectionFactory.php
Failed to connect to the database: Unsupported type:
Maybe that is actually a bug in NC or at least a function call that changed a lot recently?
Was a bug that got recently fixed.