At least in the US, my understanding is a 1975 law, the Magnuson–Moss Warranty Act, protects warranties on modified products as long as the modification didn't

At least in the US, my understanding is a 1975 law, the Magnuson–Moss Warranty Act, protects warranties on modified products as long as the modification didn't cause the issue. It comes up all the time with cars since there's an active mod community. That being said, I usually backup and "factory restore" my computers before servicing. Mostly because I don't want to hand out my password or hand over my personal data, but I expect them to test that its fixed and that's easier in a generic OS. I also think it'd be odd to hand over a Macbook Pro (or even a Microsoft Surface) with Linux installed and expect their random, low-level tech to asses things.