Here's the documentation for Kernel's EFI stub: https://www.infradead.org/~mchehab/kernel_docs/unsorted/efi-...

Like rEFInd in the sense that it replaces rEFInd. The kernel itself can be executed by the firmware directly as an EFI application.

Like rEFInd and System boot and even the inbuilt UEFI firmware of most manufacturers.

> even the inbuilt UEFI firmware of most manufacturers.

I have a <3yo laptop that boots NVME OSes fine, Windows and Linux alike ... except for the Windows feature-upgrade process, which just hangs indefinitely on the OEM logo.*

I also have a desktop whose UEFI firmware doesn't output anything to its PCI videocard, and also refuses to boot at all if anything is connected to its integrated videocard. So getting Linux installed on that silly thing at all, was an exercise in frustration.

I furthermore used to have a little "mini PC" that utterly refused to allow its UEFI boot entries to be modified at all - on top of having no boot-time video output and a soldered-on bootable storage. So I had to abandon and rollback my efforts to install Linux on it, lest I brick it. Brick, an x86-based system. Ugh!

In short, I don't respect manufacturers' UEFI firmware any farther than I can defenestrate their products.

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* I would say something about how imaging from a SATA SSD onto an NVME SSD even required a reinstall of Windows, whereas the dual-booted Linux install worked perfectly; but that's probably just Windows being its usual stupid self.