The Android Package (APK) for each production release is attached to its associated GitHub release.
However, I recommend to use an update manager app to ensure the latest updates are installed automatically or you are notified about new updates. For example:
Get SeriesGuide with Obtainium
Or manually add it using the following URL:
https://github.com/UweTrottmann/SeriesGuide
Important
Access to paid features currently requires the Google Play Store to be installed.