How can I install an app from GitHub on Android without a PC or root?
Probably there is no way to do it, if you do not have the Android SDK on your PC, necessary to compile, you can not get the apk. I do not understand the reason for your question, because the application is in the Play Store, but you can download it on your phone and follow this: https://www.androidpit.com/how-to-download-apk-file-from- google- play and get the apk. That is probably the best and only way to get this apk.
Greetings