The information you refer to is indeed outdated. For both the latest generation Fire HD 8 & 10 tablets, the Roon Remote app is available from the Appstore, which is Amazon’s version of the Google Play Store. By the way, on the latest generation Fire HD 8 & 10 tablets one can even load the Google Play Store and install apps that are not available from the Appstore, but many times these apps will not run.
I repeat: the Roon Remote works and looks great on the Fire HD tablets.
I totally agree, the additional screen real estate is well worth the higher price of the Fire HD10. You will amazed at just how well the Roon Remote app works and looks on these inexpensive tablets. Best bargain around, don’t let the Apple lovers dissuade you.
By the way, the “keep screen awake” setting is also available on the iOS version of the Roon Remote app - both iPhone and iPad.