With Mullvad there's the wireguard configuration generator that works with wg-quick and one of the options is to have it set up an iptables rule to make sure th

With Mullvad there's the wireguard configuration generator that works with wg-quick and one of the options is to have it set up an iptables rule to make sure that if the wireguard tunnel goes down it won't leak untill you actually call wg-quick down mullvad-xyz.