Bug Android signature causes apk mismatch after upgrade project to Unity 2019.4.18f (from 2019.3.0b6)

I just upgraded my Unity project to Unity 2019.4.18f from 2019.3.0b6.
I'm trying to build my Android app with the SAME keystore, but I get this when installing:

[INSTALL_FAILED_UPDATE_INCOMPATIBLE: Package signatures do not match the previously installed version; ignoring!]

The CERT.RSA files from the old and new apk are REALLY different (28 strings with the old Unity vs 33 strings with the new Unity). Problem appears only when I use Unity 2019.4.18f.

Is that a bug? What should I do?

I can't just reinstall the app because it's in the Google Play Market.

 

There's a few ways of signing an APK, I think called v2 and v3. Perhaps Unity has silently switched you over. There should be a setting in the Player Settings Publishing section to switch it back.

 

I checked this out, but that wasn't a problem with signing version.

The Owner, Issuer and Serial number in CERT.RSA has changed somehow when I use Unity 2019.4.18f

 

Is this a for-real-signed-by you APK or just one using the Android Debug key?

 

I don't know. The sign was made by an old team member quite a long time ago.

Will these screenshots be useful?

I see that in the new version of Unity the CERT.RSA corresponds to the keystore. But I have no idea how to make it work the way it did before I switched to new Unity version. As I can see, the app was sign like an Android Debug, and that's not how it should be, but now it's important to find a workaround if possible.

Development Build tick has no effect.