> Won't this also forbid virus scanners that quarantine files?

Yes. If I really _want_ to execute malware on my device, I should be allowed to do so by disabling the antivirus or disregarding a warning.

> I don't think it's reasonable to expect any manufacturer to uphold a warranty if making unlimited changes to the system is permitted

It is very reasonable and already the rule of law in "sane" jurisdictions, that manufacturer and mandated warranties are not touched by unrelated, reversable modifications to both hard- and software.

> Yes. If I really _want_ to execute malware on my device, I should be allowed to do so by disabling the antivirus or disregarding a warning.

I agree.

> already the rule of law in "sane" jurisdictions, that manufacturer and mandated warranties are not touched by unrelated, reversable modifications to both hard- and software.

Do you have any examples of such jurisdictions? I think whether this is reasonable turns on how "reversible" is interpreted. If it means "reversible to factory settings", including wiping all built-in storage media, then it seems reasonable to me that manufacturers should support this (possibly modulo some extreme cases like cars that have dozens of CPUs). But I would not be happy with having my hard disk wiped if I sent in my laptop for repairs because a couple of keys stopped working, which tells me that (to me) there remain at least two classes of "problem that should be fixed for free under warranty by the manufacturer".