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.

Revanced still works, not using it is just silly.

I’m able to play videos on my Samsung S9 with Firefox running with ublock. I never got a message.

I had this too, only thing that worked was clearing cookies and site data of YouTube, then logging in again. Another browser on the same account with the same uBlock settings worked the whole time, so I guess it's "device" bound not account bound. Since the cookie purge I don't even get the AdBlock warnings anymore.

I'm unable to watch any video despite uBlock instructions thing.