Why do people still use those?
I got a 4K Max one because it was only 35€. I want to upgrade to a shield pro successor which is overdue by now.
4k Max is so much faster than the Shield devices, i actually got upset that i invested so much money in two of them.
If you want to do this because of the full screen ads you may be too late.
You can easily change launchers on the Shield and remove all of Google’s nonsense through ADB as well though, unlike Amazon who locks down the OS very tight. Plus like another commenter said, you can just flat out install LineageOS and you’re good.