Wireguard on Ubuntu 18.04.4 (LTS)?

[Jason A. Donenfeld]

Looks like at the moment (July 20, 2020; ignore this email if you're
reading this >1 month from now) wireguard is still stuck in -proposed
on Bionic.

echo 'deb http://us.archive.ubuntu.com/ubuntu bionic-proposed main
restricted universe multiverse' >> /etc/apt/sources.list
apt update
apt install wireguard

That's annoying and odd. I'm CCing Canonical's Andy Whitcroft who can
fix this inside of Ubuntu.