Smarttube on Android TV just pulls its own APK so you just need to click Install after it downloads and opens it.
That's fine and there are tools to get that scheduled break back - even the official YouTube app has options to remind you to take a break every X min of watchtime and there are some very advanced general screentime limiting apps out there.
As you say YouTube ads aren't scheduled well and they're too short and unpredictable to even go to the bathroom during. Integrated ad reads are even worse in that regard.
I did without a TV set since I moved in a larger home. Previously I could listen to the TV anywhere in my home, now I can't so instead of pinning me in a place I moved my TV into my phone and tablets. Everything is in an app anyway and for free to air TV I got a couple of RPi 3 with a TV hat and the TVHeadend app.
And when I have guests everybody is watching something different on their phones most of the times.
F-droid enters the chat.