Try Volanda on Android

One click on «Join group». Joining the group does not install anything yet: it only grants your account permission.

Open this link and tap the «Become a tester» button. Wait until the page tells you that you are a tester. Without this step the download fails.

Says you're not a tester? Wait a minute or two after joining the group, then reload. Also check you are signed in with the same Google account you use on your phone.

Now you can install it. Open this link on your phone, with that same Google account.

Getting a "page not found"? Then step 2 did not go through. Go back to step 2, tap the button, and try again.