>>I imagine there could be regulation to force vendors keeping their old cars repairable.

Yes, but what does that mean in practice? That Manufacturer has to keep making parts for 20 years after production ends? How does that help if your entire infotainment system runs on Google's AOSS system and google just pulls the plug on it or the built-in modem stops connecting to the internet because your country decided to switch off all 3G networks(which is a real problem happening everywhere). Is the car "working" but with all apps and satnav completely blank still functional or does it need "repair" - if so, what does that repair even look like?

As a basic example - I have a 2020 Volvo XC60 with Sensus OS - all the maps are preloaded on the internal drive and they will continue working until the hardware breaks - they might get outdated but they will work. But I drove a new Volvo XC60 with AOSS and I was in the area without any signal coverage - in that case all the maps were just blank, the middle of the driver display was blank, it literally looked broken because nothing would load and the screens didn't have a good fallback for such a scenario.....which will inevitably happen to all these cars, either because they lose connectivity or because google/volvo decide to stop supporting them on their network.

You mean, ensuring repairability would be hard? I bet. And exceptions could be made where a change of technology makes aspects of the car non-functional (3G vanishing). On the other hand, the choice of contractors/suppliers, contracts with those entities, and so on would work differently with a repairability law in place.