So, here's a solution that will likely work but I'm just extrapolating based on auto industry stuffs. If the ads are driven by SiriusXM, they're likely coming over the satellite radio. The shark fin on top has several antennae in it, including the XM antenna, which is on a specific frequency band and antenna type. Find the wiring harness for the shark fin, trace the SiriusXM cable, unplug or snip it. You'll lose XM, but, honestly, based on the garbage I hear on a lifetime subscription radio these days, I don't understand why anyone pays for it, except for living in or traveling through remote areas with frequency and wanting live background noise.

Chances are it's possible they'd also try and load the ads via a paired Bluetooth phone for Internet, (maybe) if that's the case it's a little more difficult. Probably impossible on iPhone, but on Android may allow one to disable the act of shuttling data to the car stereo via Bluetooth. If Stellantis uses an app to proxy data to the car stereo, deleting the app on the phone would break it.