wac65

I have found 2018 references in forum to a 'malwarebytes app' in Amazon Appstore, and reports of people successfully using it, albeit seemingly on older models of Fire. However, I can find nothing of this kind in Appstore on my Kindle. Have I missed something between 2018 & now which means M'bytes can't be made to work on later Kindle Fire? (Only just signed up to a premium sub, so am just putting M'bytes on devices). Anything happening to enable M'bytes on Fire?? Any workarounds?? Tx