Nvidia Shield

Don't hold your breath. They seem to have their hands full just supporting the current Apps. 

Is that android based? If so, you can sideload the Dtv stream app. I have a Tivo Stream 4k android dongle with it sideloaded. Works pretty good for a bedroom tv.

Yes it is Android based.  I have heard that this can be done.  I have no idea how to do this and little inclination to learn.  I really don't see why DirecTV shouldn't make an effort to support all the main streaming boxes.  Since there are these side Android apps already doing it, it shouldn't be that hard.  I pay good money for DirecTV stream so it seems to me the responsibility should be theirs.

Can you install the "downloader" app? Should be in your app store not sure if you have google play store.

Then use the "downloader" apps browser and go to apkmirror search Directv 4.0.32.37013 --use the downloader app to download it--it will also install it for you. 

https://www.apkmirror.com/apk/att-services-inc/directv-now/directv-now-4-0-32-37013-release/

While I agree that they should offer an Android TV app, the Nvidia Shield is in no way "one of the top streaming devices" unless you mean it in the sense of one of the best.  While the Shield is popular with video enthusiasts, its overall market share is well under 1% of the overall streaming device market.

Hello, for years I've been in the same situation as I was an early adopter of the streaming app and used an Nvidia Shield on a couple TVs. It was extremely frustrating for the app not be supported on the Nvidia Shield platform. I'd have to search the internet to find a sideloaded version; and sometimes that wouldn't immediately work. In the past couple days, once again, the sideloaded app stopped working. I deleted and found a new sideload and it wouldn't work after deleting the previous version and the app icon file. I then deleted that new sideload app. I accidentally pressed the remote button that I programmed to launch the DirecTV Stream app (Newest version of the Shield remote control). An option came up and asked if I wanted to download the DirecTV Stream app. Now, in the past it would not allow me to install and give some type of error. However, today, I'm super excited to report that that the actual DirecTV Stream app actually installed and is working perfectly!!!!!!! I hope the app continues to be supported on the Shield platform.....

Maybe with the recent release of support for Android TV is the reason for your installation on your Nvidia Shield device. Will this continue? Only time will tell. As for the branded device, it is still not listed as a supported device.

When will NVIDIA Shield TV Pro be supported. It is one of a couple devices that has a 1Gb NIC. If you do not have one, You should try it out. The other one is AppleTV. It has a Directv stream app...

There is an app for Android TV devices and has been for 8 months. Have you looked in the Google Play store?

NVIDIA just bested Apple as the most prosperous corporation in the world. Its going to be hard to avoid them much longer.