I have used dongle, that's a no go, I have used USB cord also same result, then I said for sh8ts and giggles let me DL the Stem Link App in the Play Store to see if it can detect the controller and it does detect the controller connected through BT, but not in Steam Link in GFN, and just to show how much I tried i even rolled back the firmware and tried with the USB cord & then with dongle but of coarse not with BT because I just rolled back and disabled it, also made sure my steam client app was updated, made sure I had beta participation ticked, made sure Big picture mode was enabled even did a restart of steam link in GFN to check, then a complete power shut down of shield and checked but nope. yes I have Updated to enable BT and have paired with Shield, it's not detected, You say 'I have done this' then immediately revealed that you have not, in fact, done this.

So I Have Done this but in Steam Link App with dongle connected to usb port on shield the SC is not detected, Do you have any workaround, can you help pls! Why are you using the dongle? Just pair using bluetooth.

Nvidia shield tv steam link