Ublock works just fine on Firefox mobile; all you have to do is play YouTube in the browser and not the native app. Sadly, this does not resolve the "disable playback while the screen is off" functionality.
My TV is behind Pi-hole and I'm pretty sure I've never seen an ad on my TV (or while casting).
On phones... sometimes, but that's usually fixed within a day or two.
Before others crucify me for not paying for the content: I'm paying for a subscription service where most of the YouTube channels I follow mirror their content (https://watchnebula.com/). I just cut out Google as an unnecessary middleman.