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/
The person that recommended it to me said they love it and kept recommending other things I could do with it, like install an ARM version of Linux that runs Kodi as the frontend instead of Linux. I don’t mind paying the money if it’s of equal or greater quality than the Shield.