Which key(s) is it signed with? What is the hash of the corresponding unsigned artifact?
Signature verification tools should have some option which prints these things in a machine-readable format.
I did some work on reproducibility of Android apps and system images with Nix, and while defining a build step which can automatically establish these relationships sounds a bit goofy, it can make the issues with underspecified edge cases visible by defining verification more strictly. I did not do this to look for those edge cases though.
I am still working on that type of stuff now, but on more fundamental issues of trust we could start addressing with systems like Nix.
i still believe "pgp is too complex" was the most successful cia counter action after they lost the crypto wars to the people.
solving via nix only works within the flawed assumptions that end users either fully trust google or fdroid and are incapable of anything else.
PGP is too complex. I've known my way around the command line before I learned how to hand-write, and I have to look up the commands to fetch the keys and/or verify the blob every single time. Keyservers regularly fail to respond. There's no desktop integration to speak of. The entire UX stinks of XKCD 196.
Don't blame CIA for obvious deficiencies in usability.
I think you are right that UI sucks in many cases, but I think its not intrinsic to PGP - its fixable.