IANAL but I think anything that can be potentially personally identifiable, with tracking associated, would be. If you have “registered” your appliance (for that extended warranty), you have given them your details which are then associated with the device.

Say you are Samsung, you have a fridge with a camera on it that keeps track of what’s in the fridge “for the user”, so they can see inside their fridge even when not at home. Now add in some image recognition, automatically tracking exactly what’s in the fridge, how often it’s used, when it’s running low. Now you have some of the most valuable consumer data possible to sell to data brokers. That is defiantly covered by GDPR.

Only in so far that they have to notify you what data is collected, for what imaginary purpose and who is managing it. It's not personal information according to GDPR, unless combined with something else that is.

I don't think GDPR is as relevant here either, but installing a transmitter in a car that you can't turn off would be irradiating someone against their will.

France doesn't even have WiFi in schools for this reason. Hard to imagine they would allow something like this in a vehicle.

Irradiation is usually taken to mean ionizing radiation, which isn't what anyone would transmit from a car.

Vehicles have built-in hotspots and LTE modems in Europe for years now. Pretty much any german luxury brand car these days will come with builtin LTE modem for navigation traffic and other similar systems.

Also, use of your home internet modem to transmit a ISP-only open wifi is also legal according to many EU laws.

At a minimum, the transmitter would need to comply with RF exposure limits.