First step on how to get around „Ad blockers are not allowed on YouTube“ dialog?
Easiest solution for your browser (no matter the OS) is to use a verified extension like uBlock Origin available for:
Second step
Find the extension in the browser’s toolbar, click on it and select the settings icon at the bottom right of the pop-up dialog. Go to „My filters“ tab and paste the following code:
youtube.com##+js(set, yt.config_.openPopupConfig.supportedPopups.adBlockMessageViewModel, false)
youtube.com##+js(set, Object.prototype.adBlocksFound, 0)
youtube.com##+js(set, ytplayer.config.args.raw_player_response.adPlacements, [])
youtube.com##+js(set, Object.prototype.hasAllowedInstreamAd, true)
Click „Apply changes“
Filter credits: Followchain