I've been using FF with U-block Origin to visit YouTube on a daily basis. Blocking all my ads. Never been shown any ultimatum notices on the topic of ads. Wonder if my hosts file is affecting things.
But today, YTube just stopped showing content. Pages would load the correct background color but only showed gray rectangles for placeholders - no rows of thumbnails, no text. I figured it was glitching and I'd try later. But an hour later when I tried again to access YouTube, it still refused to load any video thumbnails. Showed me the site with an empty background, no alert or notice of any kind to explain the situation.
I started suspecting YT of being a little bitch over my ad blocker - U-block. So I went to see how updated UBlock was, it was version 1.53 - and the update to 1.54 was pending a browser restart. I hadn't restarted my browser for a week. Naturally I shut down Firefox and restarted - U-block updated itself to 1.54. Of course I immediately hit up YouTube and . .. it worked normally.
Everything's fine.