I am surprised this hack is almost never mentioned in "your car is spying on you" articles. Removing the cellular modem is about as important when it comes to privacy as degoogling or disconnecting your "smart" TV from the Internet.

what if it's saving all that data offline and it gets uploaded during maintenance when they connect diagnostics or something?

I was going to ask about this. Is there any documentation official or otherwise about how to take ones car offline?

Yeah, I have a Ford F150 lightning. I just pulled fuse 8. I periodically connect it so I can receive over the air updates. I hope it doesn’t store all of its data and then upload it all at once every time I put the fuse back in.