Enable Wireguard only for specific user

[Florent B.]

Hi list,

On a Linux system (Ubuntu), I would like to enable Wireguard VPN only 
for a single user on my system.

Currently by default, every packet of every user is getting though 
Wireguard.

How can I do to route packets only for 1 user ?

I think I have to play with packets marking (wg show wg0 fwmark / 
iptables owner/mark module), I tried some commands but was unable to 
success.

Can someone help please ?

Thank you.

Florent