how to change port forwards from a terminal or other ways remotely?

im travelling for several months and noticed that a port forwarding stopped being active in my router.

in past I used telnet from a ssh terminal to go and change it but that seems to no longer be available in my recent router.

Any tips/ideas on how to adjust port forwards now that I cannot get access to the web-ui remotely?

2 things:

How do I enable VPN without having access to the web UI? I have otherwise full terminal access to the network via my NAS.