I have those things in my house but it's all local using home assistant and no vendor can monitor it. I can access it remotely but only by vpn.
I'd want the same for my car if I had one. No manufacturer remote access. Any 5G module in it I would remove. Unfortunately the EU mandates ecall now but I'd just put that back in for the yearly car test.
Same here with regards home assistant.
And I agree some sort of open source solution would be nice for cars too. Especially with flood of Chinese EVs some sort of legal+technical framework is needed.
Perhaps even government agency that handles that sort of thing for you.
But until something truly secure and open source comes about - I'll trust Tesla instead.