It's for your own security, duh ;)

> presumably NSA-blessed

You have your answer

In 2012, Windows 8 stopped booting on computers without UEFI secure boot. Hardware companies weren’t enthusiastic, but they couldn’t ignore Microsoft’s demand. Microsoft published the spec for how Windows 8 would handle secure boot, and that included the crypto key that will be expiring in September. Microsoft’s spec did actually have provisions for non-Microsoft operating systems.

Linux developers didn’t all agree about whether Linux needed to do anything about Microsoft’s plan, but ultimately a Red Hat programmer convinced enough people that it would be easier to follow Microsoft’s spec than to tell new users to “turn off secure boot” if they wanted to run Linux ( https://mjg59.dreamwidth.org/12368.html ). This wasn’t a popular decision, and it hasn’t become any more popular over time, but it has worked.

I mean, NSA-blessed or not, the way this happened was not some hidden conspiracy. It was in the open. The reason it happened is all of these machines are basically made to run Windows, so they need to have Microsoft keys. Microsoft was pushing for Secure Boot, for security and "trusted computing" (evil or good, depending on your PoV,) and open source complained that this is a way to lock in users to Windows, so the compromise choice was to have them sign a GRUB shim so that Linux could just as easily be run without enrolling your own keys.

Microsoft is the trusted party because they convinced hardware manufacturers to install their keys by default; that's it. A lot of commercial/industrial/pre-branded OEM hardware comes without Microsoft's keys, they're only there for the Windows Logo.

> Why is there no charitable equivalent like a small/mini LetsEncrypt foundation for the PKI aspect of Secure Boot?

This would be pointless and erode the security of the system. Users who care can already remove Microsoft's root keys and enroll their own. There's a small corner case with UEFI Extensions / device firmware, but in this case a lightweight "sign everything" foundation would only serve to erode the security of the system. The problem space is completely orthogonal to website SSL and by and large simply good and not bad when properly configured.

> I also do not see a convincing reason it meaningfully improves security posture.

Secure boot paired with secure boot-sealed disk encryption massively reduces attack surface; with only Secure Boot-sealed keys (ie, BitLocker default), it reduces attack surface for the data on your disk to "post-boot authentication bypass or RCE" from "literally anyone or any piece of software who touches your computer or a disk that came out of it, ever." With keys sealed by Secure Boot and sealed or even just stretched by another mechanism (password, PIN, etc.), it reduces attack surface to "machine unlocked."

> MicroSlop is the trusted party to sign the shim with their (presumably NSA-blessed key)

I've been on Hacker News for an extremely long time and respect the community wish to avoid meta-discourse in general, but this kind of rubbish discourse with weird slurs and unfounded conspiracy theories is getting horrendous lately; I wish this site could more collectively move towards a productive curiosity rather than evidence-free statements based on arbitrary prejudice.

Because they were the only party competent enough to run a PKI (which is 95% policy) while Linux distros still can't agree on a single boot loader.

shim didn't exist at first. Linux was planning to go without until Red Hat's hand was forced likely because their paying customers demanded it.