https://www.latacora.com/blog/2019/07/16/the-pgp-problem/ is a good summary about the issue
Good counter discussion about PGP security
https://www.reddit.com/r/cryptography/comments/10cfslk/exactly_how_strong_is_pgp/
I would argue that latacora could be an attempt to push users into the systems that provide 3rd party service, which by definition of 3rd party service is not secure: WhasApp, Signal.
Only true P2P can be safe. PGP provides ability to send encrypted message using any means necessary: FTP, HTTP, anonymous services, USB sticks, anything.
Cargo is heavily used.
Your tutorial is the odd one.