I appreciate you taking the time to implement this and answering some questions! I have a follow up question- What's the benefit of using asymmetric encryption here? You're not signing the message ( you probably should imo ) and you don't appear to support sharing encrypted notes ( i.e a user provides one or more additional public keys that a note is encrypted for ). You're basically doing symmetric encryption with the pain of key management
It'd be simpler ( from a user and code perspective )to use symmetric encryption ( something like aes-256-gcm or ChaCha20-Poly1305 for example ) and use key wrapping to avoid encrypting user data directly and you'd have stronger crypto as a result
You're right that PGP is a valid encryption method but it's not very popular in the modern day because it's very hard to get right. Latacora has a great post on the PGP Problemand the Soatok blogs that u/litchralee linked are well worth a read too
HBO reporter that interviewed Trump a few years back
Be warned, it's extremely painful to watch: https://youtu.be/NmrEfQG6pIg