Problem with WireGuard/tun module after updating Kubuntu to 22.10

After updating my kubuntu (after that I rebooted my device) to 22.10 from 22.04 I am unable to run the wire guard:

sudo wg-quick up wg0
[#] ip link add wg0 type wireguard
[#] wg setconf wg0 /dev/fd/63
[#] ip -4 address add 10.77.28.148 dev wg0
[#] ip link set mtu 1420 up dev wg0
[#] resolvconf -a tun.wg0 -m 0 -x
Failed to resolve interface "tun": No such device
[#] ip link delete dev wg0 

I'm assuming that since WireGuard was working with the previous version of the operating system, its configuration is correct (but maybe it's a wrong assumption...), so I guess there is a problem with the tun module. When I try to check this module with lsmod | grep 'tun' I doesn't see output for it. sudo modprobe tun doesn't change anything. I also can't find the tun.ko.gz in the /lib/modules/ directory, I only see qrtr-tun.ko.

modinfo tun returns:

name:           tun
filename:       (builtin)
alias:          devname:net/tun
alias:          char-major-10-200
license:        GPL
file:           drivers/net/tun
author:         (C) 1999-2004 Max Krasnyansky <maxk@qualcomm.com>
description:    Universal TUN/TAP device driver

grep "CONFIG_TUN" -r /usr/src returns:

/usr/src/linux-headers-5.19.0-23-generic/.config:CONFIG_TUN=y

If you need any more information, please let me know. Also, sorry if anything that I provide above is irrelevant, this topic is quite new to me.

I've had the same problem. It seems to be a problem with the update(r) to Ubuntu 22.10 (my system was on 22.04).

I was able to fix it executing sudo apt purge resolvconf

Please note that I don't know if this could cause additional problems, but it worked for getting wireguard running again. Ubuntu is using systemd-resolved and normally resolvconf should only be a "link" to systemd-resolved.

Additional information may be found here.

Removing the DNS declaration in your .conf file will work to, but this is not an acceptable solution if you want to use a custom DNS server over wireguard.

In my wg0.conf file, I commented out the DNS line (because I don't like deleting anything if I can help it) and then added

PostUp = resolvectl dns %i *DNS IP ADDRESS*

to the end of my interface block

Comment or remove your DNS key in wireguard client config file

Example