Webroot behind NAT

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Using LXC containers.
How can I access the nginx server's webroot "/var/www/" when it's behind a NAT?
Unfortunately, Publii's options don't allow me to configure an SSH ProxyJump.

In the screenshot below, the server field contains the SSH command with the -J flag to enable jump hosting.
And as expected, it doesn't work. Publii only considers the IP address, not command flags.
Would it be possible to use SSH CLI options directly in the Publii interface?

[450780]

I tried with Tailscale, it works by using the Tailscale IP and 0 as the password.
But I'd like to avoid using additional software.