APK is signed with Signature Scheme V3, which is not yet supported.

There's more people impacted by the hours on the Unity thread. For some a Gradle build is working, but I'm unable to make a Gradle build for some reason. Please help :(

Managed to make a Gradle build, but now it's telling me that I should use the same key as for my previous build, so I guess that won't be an option !

I am having the exact same issue. Just uploaded fine a day or two ago, nothing changed in my process.

I finally made it work using jarsigner thanks to a tips on the Unity topic ! Today has been a crazy ride for many dev it seems :/

We were able to successfully avoid this error by uploading an apk built with Gradle (via Unity Build Settings).

Experience the same . I thought this had to do with my Java SDK update to V1.8.0_202 which i did before the build . Did you guys update ( or let it autoupdate ) Java too before ?
Anyways - i was able to fix my issue by using the jarsigner ( from the JDK bin folder ) to resign the apk with V1 scheme.
The syntax ( commandline, though i made a batch script which lets me drag and drop the apk onto it ) for this would be:

jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 -keystore <KEYSTORE> -storepass <STOREPWD> -keypass <KEYPWD> <APKFILE> <ALIASNAME>

The parts in bold ( including the enclosing  <...> ) should of course be replaced with your specific values

Thanks for the heads up, I've notified our engineering team and will update you all here once there is progress.

spacefrog said:

jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 -keystore <KEYSTORE> -storepass <STOREPWD> -keypass <KEYPWD> <APKFILE> <ALIASNAME>

Thank you spacefrog, you are awesome.
Your workaround worked for me. 

My guess would be that there was an Android sdk update that enforced this behaviour? That's the only variable in this case if you ask me. Did somebody else update there Android Studio or Android SDK after which this started happening?