This is the page where we found the info required to connect to the TM through a websocket to read the info and control the treadmill.
My treadmill is a NT 1750, 2014 model. I had friends with more recent NT 1750's and NT 2450's try a link I provided to a dumbed down version of "our app" and it did connect and work, but not sure if they were post 2017 models to be honest. Also worked on a NT X11 incline trainer for one of the other ST'ers.
I can send you a link by PM to check functionality if you know someone with a Nordictrack newer than 2017. I would think that as long as the TM has IFIT and WIFI it could work?
Sounds like Zwifit, for the purpose of Zwift, merely replaces using a footpod (i.e. transmits run speed to Zwift for display);
Setting the incline of the TM to match the course would require the game to broadcast the current grade.
T. Guertin / Spocket