Focus for Android mobile repository is located here.
Focus documentation can be found here.
Please note that Focus for Android strings shares common strings with Android-Components, just like Fenix (Firefox for Android) does. At the moment, Android-Components strings all live in the Firefox for Android folder in Pontoon - these are all the files in your locale folder that start with mozilla-mobile/android-components/
Please consider localizing all Android-Components strings in the Firefox for Android project, to ensure Focus is always up to date - or better yet, making sure you’re also up to date with all of the Firefox for Android files.
Test builds can be downloaded these ways:
Visit https://groups.google.com/g/firefox-focus-pre-release and join the Google Group (use the same Google account you use on your device to download apps from Google Play)
For Beta releases:
After you have joined the group, opt-in to receive Beta builds, (again with the same Google account): https://play.google.com/apps/testing/org.mozilla.focus.beta
Download Firefox Focus (Beta) from Google Play: https://play.google.com/store/apps/details?id=org.mozilla.focus.beta
For Nightly releases:
After you have joined the group opt-in, to receive Nightly builds, (again with the same Google account): https://play.google.com/apps/testing/org.mozilla.focus.nightly
Download Firefox Focus (Nightly) from Google Play: https://play.google.com/store/apps/details?id=org.mozilla.focus.nightly
Nightly builds can also be downloaded from here.