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.
