Earlier quoted context omitted.
Further forcing everybody to have their phone on person at all times
Depending on the implementation, you can run the app on your computer. I don't see why the iOS app wouldn't work on macOS, and there are tons of tools to run Android apps on Windows and Linux. If the actual implementations do copy the dependency on Play Integrity and other such APIs, that does become a problem (getting past that is a major annoyance on amd64 computers because there are so few real amd64 Android devic…
Wait a minute, while writing this comment, I realized that there was a guy who sort of packaged waydroid into flatpak-ish to run android apps in flatpak.
https://flathub.org/en/apps/net.newpipe.NewPipe
(It uses android translation layer??)
I am not an EU citizen but if somebody is & they want this age verification app on desktop, maybe the best way might be to support this android translation layer to convert this EU app into something that can run through flatpak and then use linux I suppose.
I mean, some of y'all are so talented that I feel like surely someone would do it if things do go this way! So not too much to be worried about I suppose :>