I am using Fairphone 2 (Fairphone OS 21.05.0-rel.1). Recent updates of system apps are also installed via Google Play Store (however, Google Play Store is deactivated most of the time and I do not use a Google account).
Two apps I recently installed have never worked properly: Threema and Familink. They crash right at start and I never get past the welcome screen. Quite often they even cause a crash of the entire phone. After such a crash the phone can only be rebooted after having taken out the battery. Does anyone have an idea what the problem might be (certain settings, bugs,…)?
Did you install from Playstore or another app store or apk directly? Did you deinstall and reinstall? Have you other google stuff deactivated that is probably needed for the apps to run properly, like play services?
All apps were installed via apk, some indirectly from Playstore via Evozi, others from different sources. Threema was installed from the official download link via apk from the Threema website. I do not recall the source of the Familink apk, but I think it must have been Playstore via Evozi.
Threema was deinstalled and reinstalled, without any effect. Play Services are activated, but with very limited access (access is granted to SMS, Storage and Telephone). Unfortunately, some few apps do not work without Google Play Services. However, I am avoiding Google as much as possible, so Play Store is usually deactivated, Google App is deactivated etc. After all, the whole point of using an alternative messenger like Threema and paying for it is to avoid Google, Facebook etc. So I would much prefer a solution that does not involve activating the standard Google apps.
I understand and do not have a real solution, as I do not use the apps, so I cannot test. If there is no solution at all, you might want to consider to install e/ OS. This comes with microG included what replaces/fakes some “important” google functions. With this OS the communication with google is very minimal to zero. It has an own play store and the stock apps are as far as I know forks of open source apps. e/OS is already based on Android 10, that would mean, switching to e/OS should work without data loss, however when you do not like it and you want to go back to FPOS this would be downgrade with def. data loss.