YMMV, but I managed to do the downgrade without uninstalling, having to re-download, or rebuild anything.
- Disable Auto-Update for BeyondPod in the Play Store to prevent it automatically upgrading back to 4.2.19.
- Open Play Store.
- Open the BeyondPod screen.
- Tap the "..." menu in the upper right corner.
- Deselect the "Auto-Update" checkbox.
- Download the 4.2.18 apk to a computer with adb installed (Not to the phone/tablet).
- Open a terminal, go to the directory where the file was downloaded and use adb to install over top of the existing app.
- adb install -r -d BeyondPod_4_2_18.apk
- The "-r" allows installing an apk over an existing installed app.
- The "-d" allows installing an older version an app over top of an existing version without removing the existing databases and files.
- Open BeyondPod, rejoice that it is not broken.
- You may want to re-check your settings and stuff, but for me, everything was working the way it was before 4.2.18 darkened my door.
FWIW, the lack of response to fix the utterly-disastrous 4.2.19, makes me very pessimistic going forward.
I'd recommend staying on 4.2.18 until the sentiments in this form indicate a new Beta os out that is not a flaming hot mess of awful. ... and even then, I'd wait a few days at least just in case. It is not worth going through that again.