No, they don't. I have been using YT Premium for years and never seen a third party ad of the type I assume you're alluding to. It is true they don't seem to e

No, they don't. I have been using YT Premium for years and never seen a third party ad of the type I assume you're alluding to. It is true they don't seem to even attempt to prevent video creators from adding ads within the video itself (explicit or implicit product endorsements especially). These ads aren't as objectionable because the incentive is there for the video creator to ensure the ad doesn't drive you away from the video, and often they try their best to make the ad entertaining in the same way their video is. This would be impractical for YT to enforce since the line is blurry between ad and content, so I don't get too grumpy about it, but I would love to pay an additional amount of money to be totally free of the ads.