How to get the real reasons for an incompatible app/.apk?

Play Store tells me: “Your device isn't compatible with this version.”
Aurora Store tells me: “Download Failed” “App not supported” 1) _Why_ do these stores think it is not supported? 2) If I get the .apk package file otherwise, how can I see the list of requirements (including minimum required API level)? (Btw, the app ([de.tafmobile.mobility.leipzigmove]) which raised these questions and took me hours to install runs just fine.)