Is there a toolchain or something for cross-compiling things into the OS? I have been asking lots of dumb questions and this is just the next one in the list.
I have finally got to the point where I can see all the information I want from a couple of mosquito_sub commands. Now I need to create an app/script to make use of it. There is no paho.mqtt on the device, nor gcc/g++, so it looks like I have to do something on my host machine and then move the app over (since I want this to run on the gateway which is a Pi Zero W).
I searched the forums and the github page, but could find to answers for this type of question. If I am yet again looking at this the wrong way, I am happy to try other options.