As an update on my attempt to sideload a previous version of the Prime Video app… apparently just by enabling Developer Tools on the Nvidia Shield, has caused every app to produce incredible eye strain.
So where previously the OS itself (version 9.1.1), and most all of the apps caused me no eye strain (Netflix, Disney+, etc), now every app causes strain.
Disabling Developer Tools did nothing to help reverse the issue. So at this point I'll have to start experimenting if whether a factory reset, or reinstalling Android, helps -- which fingers crossed will help, though I've unfortunately found neither work for AppleTv's that suddenly go "bad".
But in the end… in an effort to fix one particular app that was causing me strain, has in turn caused a device that I used nightly - as a personal escape from dealing with constant eye strain from my work computers - into a completely unusable device 😞