> following assumptions

You actually forgot the most important one: your phone should be latest and approved by google or apple.

I have an old iphone that is mint clean and fairly excellent battery, a couple months ago I wanted to travel but didn’t want to take my main in case I lose it, turned out most the essential apps won’t install because your OS is outdated, from bank ones to uber, none! Same goes if you tried to install say a banking app on grapheneos.

Those assumptions were vivid during covid, I know personally some people who happened to be in some countries where the “pass” was only through an app on a smartphone, not even printed or screenshots were accepted, only the app to get your basic human needs.