I'm going to do this soon to my GM truck.

There's a YouTube video that details the process for my exact model. Unfortunately, it's a fair bit of work.

Why do you need CarPlay or Android Auto? I'm using my car without any of them and it's perfectly fine. I get calls with Bluetooth and I can play music with Bluetooth too, both from a Samsung and an iPhone. I navigate by looking at my phone on a holder close to the wheel. The screen of the car is further to the right.

I have a different use case. I use voice controls to reply to text messages.

And it has to work with iMessage destinations that are not a phone number. I am unaware of any built-in infotainment system that can handle that. Tesla certainly cannot, as one data point.

Trying to get voice control to work reliably over bluetooth has never been anything but a laggy mess for me. A well implemented CarPlay implementation (even GM...) is way better.

I've found on some cars (i.e. Jeeps), disconnecting the antenna is insufficient. It just lowers the range of the cellular modem. If you get close enough to a cell tower it'll still find a connection to the mothership.

In my case I had to open the radio and physically remove the cellular modem. Which was thankfully on its own removable module.