Luks FDE, and install dropbear-initramfs, configure ssh authorized_keys and rebuild initramfs. Then you can access initramfs via ssh to type luks password.

They are still on the ship, and cannot get to land because of the lack of visas.

Can you access your wan ip when you are somewhere else than on your own lan?

If not, then this is probably just that your router does firewalling and nat is such order that you can access admin interface from local network via wan address.

If yes, then router has some serious misconfiguration.

Ventoy? https://www.ventoy.net/en/index.html

Wagnerians in Lipetsk, avout 300 km from Moscow

https://canada.unofficialbird.com/nexta_tv/status/1672602398915809282#m