I am not sure where else to flag this, so I apologise if this is the wrong place.
I worked through the WireGuard server guide and it seemed to go OK. I could connect my Android phone, get an IP etc. but name resolution failed, it could not contact the DNS server.
I thought may be it was a firewall problem or something else, but no. That was all fine. Turns out is was the way dnsmasq was configured (and I think this might be a default setting). "Local Service Only" was enabled and that mean dnsmasq would not serve any request coming in over the Wireguard VPN. Once I disabled that, all was fine.
As I was a bit paranoid about having a DNS server open to the world should I have something else misconfigured, I added "lan" and "vpn" to the "Listen interfaces" option of dnsmasq.
It might be worth adding something to the wiki pages about the need to check the dnsmasq configuration.