I've rent a vServer with ubuntu 20.04 and use plesk
When PHP errors happen, then no error log files are created in the log folder.
On my old vServer which has windows there wasn't such problem, the error file was created in log/php_errors/websitename/php_error.log but in linux nothing.
in the php.ini I have log_errors = on
I've seen several similar questions but they aren't helping
On my Linux server, using Plesk, the error logs are located in the logs directory, one directory up from the website root. So, something like
/var/www/vhosts/<domain.ext>/logs
Sometimes they don't immediately appear there, then they can also be found in:
/var/www/vhost/system/<domain.ext>/logs
I don't know why the logs initially don't appear in the first location.