> Is Debian using nouveau, how to check what driver is being used?
You can check /var/log/Xorg.0.log
ok
also I the issue resolved itself, I read on a forum thread that by turning off the power completely will reset the monitor. I think this issue was triggered by using the monitor on two different systems alternatively. I think one of the laptops had it running at 75Hz
Any way I am glad that it's resolved. -- Kind regards, Yudi