If you have an AirTV mini (which is awesome by the way, I love mine) , but you're not in the sling ecosystem, you just need to run two adb commands
pm disable-user --user 0 com.sling.airtvmini
(To disable and hide the app)
pm disable-user --user 0 com.google.android.leanbacklauncher.partnercustomizer
(To stop the system from trying to launch sling automatically at boot. You have to do this if you do the first one, because otherwise you'll hang at boot)
This also removes the sling logos and splash screens and basically turns your device into a non-specific ADT device.
Thanks for this. I just ordered a used AirTV Mini off of eBay to replace an old Fire Stick on my secondary TV, and I will definitely be trying this out.