First thing I did when buying my '21 Toyota was remove the fuse giving power to the cellular modem. Is it still recording my data? Of course, but that's only a worry if I go to their dealership for service. If I ever need to actually do that (recalls for example) I'll remove the DCM module from the vehicle before bringing it in. There's a very good local shop near me that I'll bring it to for normal maintenance before letting Toyota plug in to the car and download my data.

Some vehicles this may not be possible, so if this concerns you, check forums about your vehicle if it is a moving spy machine before trying this because you might end up causing the vehicle to be put in limp mode because of some BS design choices.

Toyota at least has an opt-out website. (Or at least in the US they do). You lose the ability to do stuff like remote start from your phone though. And emergency roadside service, blah blah blah. I turned off all the mapping saved route stuff immediately that let you see your previous trip average miles/KW and then turned off everything once they wanted me to pay a monthly fee for remote start and such.

I mean if you're mechanically talented enough and sufficiently motivated, you could probably rip out the digital controls and replace them with mechanical analogs, getting rid of the computer entirely. Extremely difficult, but probably doable if you know what you're doing.

That aside, we shouldn't have to do that to get out of being spied on.

No shit , this just in said anyone in security.

Is there any open source/privacy focused connected car software?

I'm shocked, i tell you, shocked!