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/
These devices are pretty popular, so if you have one it might be time to disable updates
I already did that a long time ago to my Shield TV… I downgraded to 8.2.3 and turned off auto update plus some debloat.
For me the stock launcher is the best launcher yet.
If Google can update the user interface server-side, doesn’t that mean that disabling updates still wouldn’t work for avoiding these full screen ads?