[rob_l12]

Not true. You can get 1920x1080 from the Shield TV quite happily (as per many posts in this forum, if anyone ever bothers to search).
You used to be able to get 4k too, but they changed something a while ago, and I've not been able to get higher than Full HD since.

As you say, I get a resolution of 1920x1080p, but a few days ago it had a resolution of 4K, I had to install Kdi Leia 18.9 again and now I don't know how to configure it to get that resolution. Thanks.

I don't quite know how much it ties into what the official app does, but I know there have been some recent updates to that, and every time the official app gets updated on the Shield, something seems to break one way or another...

Someone else may be able to add more specific advice on the settings, but I've tried everything and can't get more than Full HD either, and I'm fairly sure that once you've achieved that the settings are probably already right