Thanks for the suggestion. This is actually very interesting.

https://github.com/markqvist/sideband

Hive-Mail's quantum-resistant messages could be sent via Reticulum, if one didn't want them stored onchain on Hive. Still Hive would be useful, as the Public Memo Key and Public Post-Quantum Key are publicly stored onchain and can easily be fetched as needed (my code does that).

This pipeline would work even on something like Telegram, etc. The encryption protocol is built and working, one could send the messages using any rails he chooses.