You can disassemble the interior a bit (usually not too difficult) and disconnect the antenna from the comms module. Depending on the structure of the wiring harness your car uses, it may not be possible to easily do that without also removing GPS/radio functionality. Some models are now integrating WiFi/Bluetooth into the same system.
Alternatively, depending on which manufacturer your car is from, you can "acquire" the manufacturer diagnostic/service software and disable the cellular connection.
I will give a shoutout to Honda for being pretty good about this. The Civic didn't have a cellular connection at least as of the 10th gen (up to 2021). Not sure if the new '22 Civic does. Also, their infotainment systems run Android and you can root/jailbreak it - on the Civic, Accord, HR-V, and others. Again, this may change in current model years so double check before you buy. And (excepting a few years around 2016-2018) Honda also still has physical buttons/knobs for all the important controls, instead of putting everything into a touchscreen like 90% of companies do these days.
BMW has had a cellular connection in their cars for many years, but you can disable the SIM card by programming the TCB through ISTA, even on the current G chassis cars. Not sure if that completely disables Tx. Also not sure how their just released iDrive 8 system handles it though.
Alternatively you could unplug the TCB on the BMWs. That requires dropping the headliner on recent ones (annoying but not hard), and on the really recent ones I don't think you can unplug cellular only (you'll also lose GPS & some other things, potentially including WiFi/BT/NFC, I'm not sure). And it'll show a warning on the dash all the time if you unplug it.