I got a notice that was closable with an upper-left corner ❎️ after which I couldn’t reproduce the pop-up and watched videos unimpeded.
I’ll continue to report developments.
0039 PST 2023-10-13 ETA So the last two days, I’d get the YouTube warning, close it, and do the purge-update dance on uBlock Origin, and wouldn’t get the pop-up until hours later. Is that because I didn’t do it right, but the pop-up is only set to appear every few hours? Or is it because YouTube keeps fighting, and uBlock Origin keeps updating? I don’t know.
The pop-up warning is not appearing on any of my youtube devices, for which I’ve done no updates (and watch videos from Firefox for Android with uBlock. Note that I’ve turned off other adblockers, but not NoScript. Dunno if that makes a difference.