I recently uploaded an update to my app using Android App Bundle, where I had previously updated it using APKs. What I forgot is that I need a signed version of the APK for a few people who can't update through the Play Store. I used to do this by just using adb commands to pull the APK from a device after updating it in the Play Store, but with AAB there are 3 APKs (1 base, 1 language, 1 screen density), so I can no longer do that. I let Google sign it with a different signing key than the one I have in Android Studio, so I can't just generate an APK from there with the same signing key.
I did find that in the Play Console, I can download a "Signed, Universal APK" which seems to work without an issue. What's odd is that when I install that APK, there is an update for the app in the Play Store (59 kB in size, compared to the 5 MB APK). What could be in that 59 kB update?