Swedish chef of rouge monde
I was called in to help set up a new desktop. Not as a tech consultant, but as a relative. On another table was a kaput 2013-era HP Pavilion, regraded to Windows 10. Its demise had been foretold months earlier by it taking more than an hour to boot up. But by then it was in repair mode loop, tested for hours. I thought I'd take a stab and the only thing I could think of was to change the boot order in BIOS, boot a PE USB and remove the suspected malware. A first attempt didn't change anything. The second, deeper, attempt caused the computer to make me enter a 4-digit code. I believe that was defeating the UEFI-thing, but what do I *know*? Sadly, it didn't boot my USB stick, but happily it did boot to Windows 10. It was obviously a damaged Windows 10, but at least I was able to remove about 1,000 unwanted entries with mwb. Also removed one protection service that the owner had signed up for, leaving two still there. Then I connected the Internet, which may have been a far bridge. 12 hours later, much had changed on the display, including improved screen resolution, but also a different colour scheme with a yellowish-greenish cast. I thought, oh maybe there was a piece of software that filtered out blue during night time, but couldn't find such a thing on the computer. Or maybe a hardware issue had developed. Don't know the conclusion, as my time at the venue was up.
Anyway, this story is too long. No smoking gun, but it does tend to support the thought that a UEFI computer was borked by a Windows 10 upgrade. But who cares? Perhaps more importantly, it instantiates (couldn't resist) a way that might make use of perfectly good computers without tearing them down for parts: change the boot-order so drastically that it makes you input the UEFI-breaking code.
Please correct my mistakes!