The state must be abolished. In fact, all forms of hierarchy must be abolished.

I think they ship prebuilt binaries, i.e. the exact same ones you find on the Signal website

AFAIK this also applies to Tor Browser, Orbot and other third-party apps distributed by Guardian

Edit: I downloaded the files and manually verified the signatures. They are indeed the exact same files.

Because I didn’t really know how to grab an APK from the Guardian F-Droid repo, I used their S3 bucket and downloaded the Signal APK. It’s named Signal-Android-website-prod-universal-release-7.30.2.apk, which is the exact same file name as the one of the APK you can get from the Signal website.

I then used keytool to print the signature certificate fingerprint: (renamed the files to make it less confusing)

keytool -printcert -jarfile signal-website.apk

Signer #1:

Certificate #1:
Owner: CN=Whisper Systems, OU=Research and Development, O=Whisper Systems, L=Pittsburgh, ST=PA, C=US
Issuer: CN=Whisper Systems, OU=Research and Development, O=Whisper Systems, L=Pittsburgh, ST=PA, C=US
Serial number: 4bfbebba
Valid from: Tue May 25 17:24:42 CEST 2010 until: Tue May 16 17:24:42 CEST 2045
Certificate fingerprints:
	 SHA1: 45:98:9D:C9:AD:87:28:C2:AA:9A:82:FA:55:50:3E:34:A8:87:93:74
	 SHA256: 29:F3:4E:5F:27:F2:11:B4:24:BC:5B:F9:D6:71:62:C0:EA:FB:A2:DA:35:AF:35:C1:64:16:FC:44:62:76:BA:26
Signature algorithm name: SHA1withRSA (weak)
Subject Public Key Algorithm: 1024-bit RSA key (weak)
Version: 3

keytool -printcert -jarfile signal-guardian.apk

Signer #1:

Certificate #1:
Owner: CN=Whisper Systems, OU=Research and Development, O=Whisper Systems, L=Pittsburgh, ST=PA, C=US
Issuer: CN=Whisper Systems, OU=Research and Development, O=Whisper Systems, L=Pittsburgh, ST=PA, C=US
Serial number: 4bfbebba
Valid from: Tue May 25 17:24:42 CEST 2010 until: Tue May 16 17:24:42 CEST 2045
Certificate fingerprints:
	 SHA1: 45:98:9D:C9:AD:87:28:C2:AA:9A:82:FA:55:50:3E:34:A8:87:93:74
	 SHA256: 29:F3:4E:5F:27:F2:11:B4:24:BC:5B:F9:D6:71:62:C0:EA:FB:A2:DA:35:AF:35:C1:64:16:FC:44:62:76:BA:26
Signature algorithm name: SHA1withRSA (weak)
Subject Public Key Algorithm: 1024-bit RSA key (weak)
Version: 3

The fingerprints are identical.

Another edit: I just noticed that Signal even has official instructions for checking the signature on their APK download page. They use apksigner instead of keytool, but it’s basically the same process.

It’s probably not an official thing. F-Droid can’t distribute apps in the official repo via their own policy if the developer doesn’t agree. Third-party repos like Guardian can.