In a lot of cars its the infotainment system. In my car there is an information system that runs in tandem with the stereo and feeds information to the dashboard. Pull that out and it cannot communicate to the manufacturer. However pull that out and your stereo no longer works. There are after market stereos but nothing that fits nicely in your dashboard AND has a usable UI (there exist tesla-style giant LCD screens but the software is what you would expect from an unlicensed chinese manufacturer)
Almost nobody with a 5+ year old car goes to a dealer though, so while Ford can download this, in practice they never will. One the care case someone does, the tool will download data, but Ford will no longer be maintaining the system it uploads to anymore.
If you need ford required service your nondealer has to pay for the ford system. That ford system that hooks to your ODB2 port calls back home and sends all the APIC data.
Have you ever gotten a new key made for your Ford? That’s one of those services which requires a ford system. It’s the same system ford has used for almost 20 years now. But you are correct, it will no longer be maintained for random reasons…
In a lot of cars, this will be an identical board (since the manufacturer only wants to certify one vs many of them). This gives you at least a start of what to look for.
If you do something to Part A, it doesn't void the warranty to Part B unless the manufacturer can prove it did.
If you unplug the cellular antenna, that should not affect the physical characteristics of the engine for example.
Companies can claim anything they want such as 'warranty void if you remove this sticker' (or not responsible for damage), but that does not automatically make it true. A Supreme Court opinion even said "warranty void if removed" stickers might even be illegal, but they would need a case to come to them before they can determine that.
