I have a chromecast with Google tv and could natively install a launcher from the playstore and non playstore apps from file managers. I have no ads. Autoboot to my streaming app. Remapped remote buttons. All without using adb
Android TV is very limited compared to regular Android. It's hot garbage. Connecting a Bluetooth headset requires navigating through 4 levels of menus, it is missing several accessibility features such as audio balance settings, and has ads on the launcher. On top of that, it runs like shit even on a 4 core CPU.
The entire android tv UI is garbage. Lose internet while Disney plus or Netflix are loading? There's a good chance you need to force close them to make them work again. That's like 5 menus deep and doesn't make a lot of sense how to get there. Long press to bring up app info? Yeah right!
And the hardware is often total junk. There's a reason people still recommend the Shield, a device which is 5 years old and runs Android 9.
People here don't want to hear it, but using an Apple TV will ruin the experience for everything else from a hardware perspective. Software aside, of course. There's no reason for Android devices to exist on such sub par hardware. And yet....
You can with some tinkering. You can uninstall the default launcher with ADB shell and some Android TV show select launcher options when more than 1 is installed.
Usually you have to either disable the default launcher with adb or you need to remap the home button to open a dofferent launcher.
I always go the adb route for everything. I also have UART access on my TV, so I can disable the setup wizard and avoid logging into anything or accepting any EULAs.