Edit: I opened another tab in a separate Firefox container and didn't get the pop-up. I believe I read this shit being account-based when the first reports of Youtube's anti-adblock measures started making the rounds and it seems to be the case still
People kept telling saying ubo+ff was already up to date, but it hasn't worked for me either.
I updated my filters and the pop-up hasn't come back, but I fully expect it to rear its head later.