For those of us who are too cheap to pay the subscription:

On my iPhone I almost never see YTube ads. I don’t use the YTube app and instead I install Chrome and watch YT that way. I lose notifications—which is perfect for me, since I don’t want many notifications on my phone anyway.

This might also work in Safari but I haven’t tested it.

On Android, Firefox with sponsorblock. I do pay for Premium though. In since YouTube Red.