Actually, that's not even relevant. For the last several years, I've been developing WireGuard on top of the latest kernel from Linus, while maintaining a "compat" layer to seamlessly backport it using horrendous tricks with the C preprocessor. That's allowed me to keep the codebase clean and ready for mainline Linux, while enabling people to use it on all the old kernels. I've maintained this backport layer for every kernel since Linux 3.10, including the RHEL-7 and RHEL-8 ports. This has been quite a lot of ugly work, but ultimately worth it as its given us enormous amounts of testing in odd environments, so what's shipping now in Linux 5.6 is rather polished, as opposed to being brand new and untested. We maintain some CI for this, too, testing lots of kernels and architectures. Scroll down to the "wireguard-linux-compat" section of https://www.wireguard.com/build-status/ to see.

All this is to say that there's not really much work that needs to be done by Ubuntu or RHEL or anyone else that wants to ship WireGuard -- the backporting stuff has already been done and is fairly widely deployed by now.