VPN without openvpn

Hello to all.

By creating the VPN on the Turris Shield, and then using OpenVPN on the client it all works.

But…
I need to create a site to site VPN using the Pre-shared key (PSK) instead of using an openvpn certificate.
So create a VPN that doesn’t need OpenVPN.

How to do?

What kind of VPN do you mean?