Try to upgrade your build tools version, we are using v4 signer.
Using build-tools 35.0.0, apksigner 0.9, when verifying your APK: INFO: SourceStamp: No digests available in the source stamp for signature scheme: 31 Are you getting a different result? Which build tools version?
Using --verbose is now showing the certificate information. However, it gives false for Verified using v4 scheme (it's true for v3.1 scheme)