Well I guess jewtube decided to roll out anti adblock messages before watching videos. I just got my first message saying "youtube does not allow ad blocking software".
God forbid I want to watch something and not have my eyes and ears assaulted by Pfizer/McDonalds/Disney/etc. at max volume.
If they actually ban adblock I'll just stop using it entirely. It's not usable without it, and it's not worth the hassle to get around it.
It will only last a few days. They seem to be testing this out on groups of accounts, or maybe groups of IPs, in a sort of rolling beta. It's happened to me three times, then it disappears after a few days. At first you could circumvent it with Ublock, but it seems they've found a fix for that. Whether they actually roll it out permanently site-wide may depend on the number of people they can bully into whitelisting them with these tests.
Youtube's been trying different stuff in recent months. Used to be ads simply didn't exist with an ad blocker. Then videos stopped loading at all for a couple days. Then for a while only the audio of the ad played but not the video. And now I just get a black screen, no audio or video, for a bit and then the actual video starts.
All kinds of sites have tried blocking ad blockers. I don't think anyone managed to keep it up. It's a constant game of cat and mouse and in the end they all seem to realize it's not worth the effort to keep updating their system.