Open qbittorrent port on proxy rpi3?

I run proxy through RPi3b+ that is installed in another country. I want to open a port on RPi that is being used by qbittorent on main machine which is 6881. Is there any way to do it?

I have used ufw enable 6881/tcp but it seems not to work. And I tried miniupnp but it fails to ind IGD which must be there cause router does have UPnP tailscale port open automatically. Am I doing something wrong?