Ninja template issue installing NordVPN module

I’m trying to modify this docker image Ubuntu Desktop LXDE VNC to install NordVPN plus a few other modules. So far I’ve been able to successfully install things like Java however, with NordVPN I get the error:

Setting up nordvpn (3.3.1-3) ...
[ERROR] Unknown environment `sh'
dpkg: error processing package nordvpn (--configure):
 installed nordvpn package post-installation script subprocess returned error exit status 255
Processing triggers for systemd (237-3ubuntu10.29) ...
Processing triggers for libc-bin (2.27-3ubuntu1) ...
Errors were encountered while processing:
 nordvpn
E: Sub-process /usr/bin/dpkg returned an error code (1)
The command '/bin/sh -c wget -qnc https://repo.nordvpn.com/deb/nordvpn/debian/pool/main/nordvpn-release_1.0.0_all.deb -O /nord.deb  && dpkg -i /nord.deb    && apt update   && apt install -f -y nordvpn' returned a non-zero code: 100
Makefile:18: recipe for target 'build' failed
make: *** [build] Error 100

My .j2 file (same as https://github.com/fcwu/docker-ubuntu-vnc-desktop/blob/develop/Dockerfile.j2) except a couple of lines similar to this:

# NordVPN
RUN wget -qnc https://repo.nordvpn.com/deb/nordvpn/debian/pool/main/nordvpn-release_1.0.0_all.deb -O /nord.deb 
    && dpkg -i /nord.deb 
    && apt update 
    && apt install -y nordvpn

I don’t know how I can see what commands are being run during the ‘post-installation’ phase, but I’ve ran this on a clean ubuntu vm and a lubuntu but that installs fine and doesn’t indicate what could be going wrong.
I’ve tried googling the error, but nothing of significance is returned – I can’t run the ‘apt install -y nordvpn’ within the docker image as I get security warnings and the inability to find the nord host. (I assume this is something the original developer has baked into their final docker configuration to reduce issues).

Any advise would be greatly appreciated as I’ve been trying this for a few hours now with no luck.

Source: StackOverflow