Hey folks, just to confirm, the YouTube issue happens to me as well. Since about last Thursday (I think), static ads have been appearing before roughly every other YT video I watch. They have a countdown timer in the bottom left corner.
About 50% of the time, when I click "Skip Ad", the browser tab will completely lock up. The tab's content freezes and stops responding to input. This is on Linux Mint 19.3.
I need to then copy the video's URL from the address bar, open it in a new tab and retry skipping the ad, which usually works.
I am always logged into YouTube and I don't have a Premium account.
I checked Opera's "Privacy protection" settings and there are 3 "recommended lists" to choose from, all of which I have enabled. There are two more under "Other lists", but they don't seem to relate to YouTube.
Has anybody been able to block these ads, and if so, how did you do it?