There isn't one cryptosystem that does all these things. For messaging you want a carefully-defined notion of forward secrecy and post-compromise recovery, along with a careful decision about repudiation/non-repudation (1990s cryptography doctrine would suggest you just always want nonrepudiabilty, which turns out to be disastrous for privacy). For backup, you want deduplication and content addressing. For packages, you want transparency logs. You almost never want long-lived keys, but you often want identify binding.

PGP solves basically none of these problems, and offers instead a 1998 API (I'm not kidding, I thought about what year to pin it at) to basic cryptography primitives.

https://www.latacora.com/blog/2019/07/16/the-pgp-problem

Recommendations: https://soatok.blog/2024/11/15/what-to-use-instead-of-pgp/

We don't need to keep elaborating or re-litigating the same discussion. The PGP idea of "one tool to rule them all" is a terrible cryptography design, and the world is better off the sooner we stop trying to make it work.