I picked up a tablet from Amazon in a recent sale. I noticed the device (Fire HD 10 2021) is running Fire OS 7. (7.3.2.6 as of now) which is based on Android 9.0 (Pie). I have heard the tablets stay on the base version they have been shipped with to deliver a stable performance during the expected lifespan of the device. Sounds okay, however, I wonder if the most current version of Fire OS for a given device is as secure as the latest (supported) version of vanilla Android considering the version gap and vendor's update practice. The biggest security factor is probably still the user behavior but the platform and the eco system plays a role too. I tried to look into some related security questions to come to a conclusion but could not find good information, e.g. Are fixed Android exploits that affect older versions (back) ported to Fire OS? Is the average number of open vulnerabilities similar or higher? I am at risk if I am using Fire OS on an older device or should I consider rooting it and replacing the OS after 2-3 years? Can someone shed some light on this matter?

I'm using Fire OS 7.3.2. I'm trying to set the "Automate" app as a Device admin, but when I click "Grant as device admin" it doesn't do anything. So I then tried to use ADB commands but it only just said "Unknown component". Can someone please help?