Theres's nothing stopping you from having a JID username@example.com and an email username@example.com. XMPP and e-mail are different protocols that operate on different ports, so their respective clients will figure out how to send a message to the correct server.
Now, if you're asking how you can set something like this up, then you independently have to set up an XMPP server and an email server on the same domain. Or use some kind of email to XMPP bridge.
Selfishness is not a historical necessity of human nature, but rather one component of human nature as it exists in the current historical moment, shaped by current sociological, religious, political, and economic structures.
Attributing selfishness as an inherent part of human nature and letting that underpin your misanthropy is wrong on two accounts:
I suggest you do some reading to better understand the idea of human nature.
A favorite of mine is Elementary Principles of Philosophy.
Yeah I don't think there's any one client that necessarily hits all the boxes. As long as you stick to Movim, Dino, Gajim, and Conversations you should pretty much be set for most things.
Maybe the only solution is to roll your own client 😉
If you're seriously wondering then I'd highly recommend reading Daniel Guerrin's Fascism and Big Business. And Antonio Gramsci's Prison Notebook, particularly the section The Problem of Political Leadership in the Formation and Development of the Nation and the Modern State in Italy.
Mullvad implements Wireguard under the hood. I think they have some OpenVPN endpoints, too.
From Fascism and Big Business by Daniel Guerrin
From Gramsci's Prison Notebooks
A tool to make bootable Live USBs out of operating system ISOs.
Edit: the nose looks nicer with quotation marks instead of the underscores on top
.--. ..**''**.. .--.
: .` `. :
`./ _ _ \.'
( (_) (_) )
_.-`. .'-._
/ `-./""\.-' \
`--'
Here's how it looks in KWrite:
That is a feature added to the XMPP web client Movim recently. https://mov.im/community/pubsub.movim.eu/Movim