The e-prescription app does not support alternative app stores or platforms such as F-Droid. If you are using a "free" Android operating system and/or do not want to use the Google Play Store, you can download the Android e-prescription app directly from gematik's github server. Simply open the link in the browser and select the download of the APK file. Please note possible safety instructions on the smartphone. You can download it here: https://github.com/gematik/E-Rezept-App-Android/releases