@lemlowack It may be because of your pc not being very good. Mine works perfectly on all devices. Maybe reinstall opera or use an older version for the best performance.
If you have the problem that your Opera GX browser shows a white border around it, the solution is very simple, you will have to close the browser and run it as administrator. You can configure it to always run as administrator from the preferences tab by right-clicking on the program.
@achroi ok since I can't edit before 30 minutes passed I reply to my self, the Adblocker seems to be the problem, I just disabled it and YouTube works fine again. so Something that should be fixed is that the Adblocker doesn't cause this issue,