NVIDIA Shield Pro (the 2019 model is the latest version) with a couple of customizations STILL is the absolute best for avoiding ads.
It is the most powerful outside of the latest model AppleTVs, but with the added benefit of being completely customizable.
Personally, I HATE ads, so I use a combination of customizations to eliminate them completely.
A custom “launcher” - this is a little weird to wrap your head around if you’re not familiar with Android OS devices, but it basically means “replacing” what you see when the device turns on. A few years ago, Google couldn’t help themselves and started adding more and more advertisements to their “home page” for the Shield’s default launcher app, so I switched to the “Wolf” Launcher and have never changed, though I would probably recommend “FLauncher” now since you can still (at least last I checked) get that directly from the Google Play Store without any “side-loading” (which means to install things from non-Google sources)
I love YouTube, but hate ads, so I downloaded and installed a 3rd party YouTube client called “SmartTube Next” - which although DOES require a side load installation, COMPLETELY ELIMINATES ALL ADS, AND in-video sponsorships, and even intros and other annoying filler content in some more popular videos.
The side-loading part makes things a little more scary/difficult to setup but I promise it’s worth it and there are always updated videos online on how to do this safely and securely.
I just set up like 8 of these things a few weeks ago for my brother and he loves it. Nothing is laggy or slow, no ads, and it integrated into his Smart Home stuff effortlessly.
One last note - a custom launcher can replace the default one (rather than run alongside it) by grabbing and installing “Launcher Manager” - another side-loaded app.