My elderly mother has one app to watch some programming, and I installed it on an Amazon Fire TV stick, but even that is too complicated for her to navigate, due to all the recommended content. Is there a simple solution, where I can have minimal apps and a simple UI?
Roku
Just buy a Mibox for her and only activate the app row.
you could, potentially, just sideload an app that auto launches the app when she turns the device on.
Then it would go right into the app she wants to use - if she gets stuck, turn it off and then back on.
Haven’t tried this but an auto launcher should do the trick. Boots right into the app.
http://aerialview.tv/mobile/2018/05/29/make-any-app-launch-on-start-up-on-your-amazon-fire-stick/
Mi Box S
This link shows you how to add a custom launcher to Firestick:
https://m.youtube.com/watch?v=j3INr2i0H8A
ATV launcher pro would let you hide all apps except what she needs.
One possible solution for even more simplicity would be to set Kodi as the launcher, and have it run the relevant app on start up. Maybe trickier to get that to behave properly though...