Well, that is actually not true. I run both, Sonarr has to be updated manually but Radarr does it automatically. To the extent that I had to double check the version as I never have to check that software. And I have the latest release, and the log confirms that it never has a problem with code signing, never has. And I’m on the development branch, so I’ve had 5 updates so far since the 6th of October.
Maybe they have an Apple account, I don’t know how they do it, but they don’t have this problem.