Unrelated, but the same result is achievable by using Safari and 1Blocker for the people who don’t feel like installing another browser but are tempted by the mobile, ads free YouTube experience on iOS
btw: it’s also possible to go to fullscreen mode, then go directly to the home screen so that the pop-over player is activated, then the video keeps playing while the screen is looked, with controls working from the lockscreen.
Unrelated but you can also block ads with the FF mobile browser using ublock origin. I understand playing videos with screen locked is a big plus for brave though.
Does it block ads?