it can actually work with 4.19 and the unstable repo.
I'm using 4.19.105-v7+ (to solve a macvlan bug in the default .97 and it works.
It's a pain to install the headers on raspbian though
That's what I've been doing, but I would like more official support for something as critical as VPN. I don't forward many ports across my NAT, so I really rely on the VPN to be rock solid. I am considering getting a second raspberry pi and running wireguard on two ports on two pis for redundancy (the ability to fix stuff after a bad update or me breaking something).