[Shield Tablet General] drowd:
Full Disclosure: I'm an Android development scrub, but I'm pretty familiar with flashing various ROMs, kernels, etc. I have long since moved on from the Nvidia Shield Tablet as a daily driver, but I had a custom 3D printed mount for the tablet and controller (this one: https://www.shapeways.com/product/WFSFW85NB/nvidia-shield-2015-controller-nvidia-shield-tabl )that is perfect for portable gaming. Enter Stadia, with all it's flaws, I wanted to put together a quick how-to to save some people time that want to do something similar. There are probably easier ways to do this, but this is what worked for me.

The end goal is to follow the XDA Stadia guide, but I ran into a few issues along the way: https://www.xda-developers.com/enable-google-stadia-any-android-smartphone/

If you already have Magisk and MagiskHide Props Config enabled and working, the guide above is all you need (except for maybe Step 8)

Step 1) Get a custom ROM flashed that still has support for Nvidia software. This is probably only important if you plan to use the Shield controller, though. I used this one: https://xdaforums.com/shield-tablet/development/rom-hyperstock-mra58k-shield-k1-v1-5-t3522897

Step 2) Make sure that Magisk is working and install the MagiskHide Props Config module from within Magisk Manager

Step 3) Verify adb tablet connectivity 'adb devices' and enter a shell 'adb shell'

Step 4) At this point, you want to go through the MagiskHide Props Config text menu by entering 'props' at the shell. However, Props Config requires busybox, and it recommends busybox by osm0sis as a download in Magisk Manager, but I could never get it to detect busybox. Spent a lot of time on this, and the best I could tell from Google is that the ROM debloater was somehow interfering with Magisk busybox, but YMMV. If you don't get this error in your ROM, skip ahead to step 7.

Step 5) Since the Busybox by osm0sis Magisk Module didn't work, I installed one of the busybox implementations on the App Store: https://play.google.com/store/apps/details?id=stericson.busybox

Step 6) Once you open the app, it will ask you to install, but warns you that without the pro version, the busybox install won't survive a reboot. That was fine for me as I just wanted to see if MagiskHide Props Config would work, and it did. Now I could move on to running the script by 1) 'adb shell' and 2) 'props'

Step 7) For this step, the XDA guide works pretty well. The only change is that 'add/edit custom props' was option 4, not 5 as it indicates in the guide, but YMMV: https://www.xda-developers.com/enable-google-stadia-any-android-smartphone/

Step 8) Next major problem -- after you reboot, you will get a constant window notification that "Nvidia Gamecast Service has stopped" and this makes the tablet entirely unusable. The solution is to disable the app with adb and reboot. Once again, connect the shield to a laptop, enter the adb shell, and then disable this service with the following command in adb shell: "adb shell pm disable-user --user 0 com.nvidia.nvgamecast". After you disable, make sure to reboot your tablet.

And that's it. I imagine the Venn Diagram of people that have an Nvidia Shield Tablet + an Nvidia Shield Controler + Stadia is probably quite small, but this was enough for me to dust it off and get some new life out of it.