For me it’s in the playstore settings. Not sure for the onn. So I go to the playstore, click my avatar top right, click manage apps and devices, then click the turn on play protect scanning section, then the gear icon, then turn off auto updates. That way I have to update manually. Not sure if Google will change that though.
Google sends very few updates to the ONN 4K Boxes. They are not blocking anything yet it’s all just speculation. Can’t see why you would not want to get helpful updates at this point.