I just got blocked by YouTube on LibreWolf today but not Firefox. The ad blocking related extensions I have are uBlock Origin, Privacy Badger and Malwarebytes. After 15 minutes of resetting uBlock Origin settings, I’ve decided to try turning them off one by one, I found that it was Malwarebytes that triggered it. Even when I whitelisted Youtube but it didn’t work, I have to disable the extension to fix it. It looks like it isn’t YouTube don’t want you using adblocks, it’s YouTube don’t want you to block scams and malwares.