EDIT:
So according to this thread, this is a Google related change and not Nvidia?
In which case, similar to the banner issue from a previous update, you can get a different launcher (see comments for FLauncher) to avoid it
https://www.reddit.com/r/ShieldAndroidTV/comments/181vh4t/ads_at_full_screen/
But I bought the hardware, why do I want full screen ads on bootup and between launching every app?
Imagine a laptop playing a full screen ad every time you closed word to open up your web browser. Just rather thow my laptop at the wall.
Windows 11 (in certain markets anyway):