I am switching my themes, do I need to update any liquid code in my new theme to keep the app working?

No, the app doesn't interact with your theme code at all

Written by ASR

Updated over a week ago

The app doesn't use any theme code to work. It only connects to your shop as a carrier service in your shop's shipping settings.

So this means if you are updating or moving to a new theme there is no further action you need to take to keep the app working as usual.