Some have a fuse you can pull for the modem, without disabling anything else. Others you can pull the antenna, and add a resistor instead.
e.g. http://sandsprite.com/blogs/index.php?uid=7&pid=462&year=201.... I think this head unit is shared amongst Chrysler vehicles, so Chrysler is an option (but then you'll have two problems).
The interesting part is that even though the antennas were disconnected, there was enough RF making it's way through the plastic sides of the module to give him 2-bars of signal strength. Wrapping it in grounded aluminum foil still allowed enough signal strength for transmission when they were very close to a cell tower. GPS signals were also being routed to the communications module over the car's network from the entertainment module (not sure why the entertainment module needs a GPS antenna or location data).
Ultimately they opted-out from data collection using the Lexus app and will rely on legal protections - in addition to disconnecting the antennas.
https://www.clublexus.com/forums/gx-2nd-gen-2010-2023/983214...