I tried to replace a dumb phone with an android phone mainly because the screen size was larger and its possible to make the text much much larger than default.. But I failed .. with grand grandma.
One of the troubles was the top system bar with all the controls, airplane mode and such, she accidentaly put her phone into airplane mode, turned on do not disturb etc. I tried some custom launchers hiding it, but it was not 100%.. Then she did not see the battery status or missed calls status.. I tried several widgets to display the battery status.. worked..
Another trouble was, that the phone app did not look the same each time she started it. It was showing the last state. Recent calls, etc. But we needed to always show just the favourites. I found different phone app that was quite ok.. but not 100%. She also did not understand that picking up phone is different if it rings while the phone is locked or if it rings with unlocked phone. Sometimes a full screen ringing appeared, sometimes only the small widget below the title bar. This was very confusing to her.
Swiping gestures.. no way. So I turned on the navigation buttons. She did not understand what is the difference between the back button and the home button. I tried to get rid of the "recents" button, but i was not successfull. The last thing is that she was forgetting to charge every other day.. I failed.