Hmm.

There are some software packages that will permit one to create virtual controllers under /dev/event/event* and use physical controllers as inputs to the virtual controller's inputs, while hiding the original controller. That may be more-involved then you want, but it should permit for that; wouldn't need to have a trackpad on the virtual controller, or could not pass through events. Haven't done this recently.

If you're just talking about in Steam, Steam Input apparently sounds like it has an option to disable controller trackpads at the Steam Input layer, from a quick search.