1 Varies by brand and model, but usual a cellular connectivity module, aka telematics. Some cars you can simply pull a fuse, some make it hard
2 Killing the telematics by pulling a fuse can cut off inbuilt navigation functions or the entire display and control system depending on how integrated it is. Work arounds can include pulling the GSM module or faraday caging the antenna.
Need specific models for more specific answers.
Slanted but accurate.
Neither Lemmy nor Reddit are private, they’re both publicly indexable (google et al).
On the other hand reddit goes to a lot of trouble to capture everything about you. Lemmy is not quite that greedy.
One is a for profit willing to do whatever it takes to make a buck. The other is FOSS and run by volunteers.
I think it’s pretty clear which is the greater threat.