Comment 2 for bug 1910404

Actually, got exactly same error from official repositories.

Here is the error after instaling without ppa:

Setting up wireguard-dkms (1.0.20201112-1~16.04.1) ...
Loading new wireguard-1.0.20201112 DKMS files...
First Installation: checking all kernels...
Building only for 4.4.0-31-generic
Building initial module for 4.4.0-31-generic
Error! Bad return status for module build on kernel: 4.4.0-31-generic (x86_64)
Consult /var/lib/dkms/wireguard/1.0.20201112/build/make.log for more information
.
Setting up wireguard (1.0.20200513-1~16.04.2) ...
root@server:/etc/apt# cat /var/lib/dkms/wireguard/1.0.20201112/build/make.log
DKMS make.log for wireguard-1.0.20201112 for kernel 4.4.0-31-generic (x86_64)
Qua Jan 6 11:47:52 -03 2021
make: Entering directory '/usr/src/linux-headers-4.4.0-31-generic'
  LD /var/lib/dkms/wireguard/1.0.20201112/build/built-in.o
  CC [M] /var/lib/dkms/wireguard/1.0.20201112/build/main.o
  CC [M] /var/lib/dkms/wireguard/1.0.20201112/build/noise.o
  CC [M] /var/lib/dkms/wireguard/1.0.20201112/build/device.o
  CC [M] /var/lib/dkms/wireguard/1.0.20201112/build/peer.o
  CC [M] /var/lib/dkms/wireguard/1.0.20201112/build/timers.o
  CC [M] /var/lib/dkms/wireguard/1.0.20201112/build/queueing.o
  CC [M] /var/lib/dkms/wireguard/1.0.20201112/build/send.o
  CC [M] /var/lib/dkms/wireguard/1.0.20201112/build/receive.o
  CC [M] /var/lib/dkms/wireguard/1.0.20201112/build/socket.o
/var/lib/dkms/wireguard/1.0.20201112/build/socket.c: In function ‘send6’:
/var/lib/dkms/wireguard/1.0.20201112/build/socket.c:139:18: error: ‘const struct ipv6_stub’ has no member named ‘ipv6_dst_lookup_flow’
   dst = ipv6_stub->ipv6_dst_lookup_flow(sock_net(sock), sock, &fl,
                  ^
scripts/Makefile.build:258: recipe for target '/var/lib/dkms/wireguard/1.0.20201112/build/socket.o' failed
make[1]: *** [/var/lib/dkms/wireguard/1.0.20201112/build/socket.o] Error 1
Makefile:1403: recipe for target '_module_/var/lib/dkms/wireguard/1.0.20201112/build' failed
make: *** [_module_/var/lib/dkms/wireguard/1.0.20201112/build] Error 2
make: Leaving directory '/usr/src/linux-headers-4.4.0-31-generic'