Gregory's Server@briankrebs According to https://www.virustotal.com/gui/file/c1bcbc47df990fdd6df4a22821921020c7a10a4288a5a8bb5a5b167289b80ee8/details the Windows installer from https://www.virustotal.com/gui/url/4ea2cb529e36f869994c7b1b7d793be02ce94dcccd0a7ba4f5f674f845446d11 is digitally signed. Not sure if that, or any of the signers, count.
@briankrebs On the other hand, https://updates.signal.org/desktop/apt/keys.asc signed https://updates.signal.org/desktop/apt/dists/xenial/Release as https://updates.signal.org/desktop/apt/dists/xenial/Release.gpg, which in turn matches https://updates.signal.org/desktop/apt/dists/main/binary-amd64/Packages and https://updates.signal.org/desktop/apt/pool/s/signal-desktop/signal-desktop_7.24.1_amd64.deb