We have a HiSense Android TV (most are now Google TV, but they're essentially the same). There are ads by default, but you can install a custom launcher with no ads, so the experience is much better.
I use Projectivity launcher and it looks nicer, has no ads, and it's much faster and more responsive.
As soon as I figured out how to install a custom launcher, I researched how to disable ads similarly on our Roku TVs and discovered all of the secret menus that could have disabled them, except they no longer work.
So the Roku level of lockdown on their custom OS is much worse now versus an android-based OS.