On an Android phone you can use firefox, ublock origin and youtube in the browser, too. It also supports playing in a floating window (fullscreen the video and then switch app from firefox to something else).
I noticed this is starting to be less effective. Now and then an ad creeps through the protection barrier. First time it happened to me was exactly at the moment I was demonstrating someone that I really do have an ad-free internet experience :/
i'm using vanced and it works really great, the only ads that i rarely see are the "recommended promoted video"