The RazPis are a bit weird OS wise. They don't use the mbr. To boot up, the 1st partition must be FAT. There's a github project that loads a pile of mainly firmware files for various stuff and they all do config & fixups before ever thinking about loading a kernel. If any errors occur, or the sun goes behind a cloud or your sdcard goes west (again), You need a binary backup.

The RazPi 0,& 1 have effectively no fpu, so they need maths emulation (=soft float). The Razpi 2 can be compiled hard float (=use the FPU) but it's 32bit only. The RPi 3 & 4 are 64bit, but 64bit ports of programs are not as common as for X86_64. For instance DRM works on 32bit, but not on 64bit.

So if the distro is not distributed as a binary image, it won't work on a RazPi. That said, there's some surprising stuff available. For instance, everyone selling usb wifi units seem to use this weird Ralink chip which got a driver in 2012. But the main Arm kernels have bent that code straight and it works. So the way to find out about support is to email the distro mailing list about support.

That sounds like a UEFI to me.

It's actually not. Nothing has firmware. So the GPU downloads it's firmware via serial connection, then grabs the cpu or SoC firmware, then something divvies up memory (for cpu & gpu), then they load more firmware, there's a config.txt to be read and it sets up the board, blah de blah, finally it reads cmdline.txt, which is the kernel command line, checks config.txt for the kernel name, and loads that. Does that sound like UEFI?

No worries. As usual Jeremy is "on the ball" - https://www.linuxquestions.org/quest...es-4175682809/

Once again my point is made - Firmware == Software. The distinction is minimal.

Well, the distinction is that software runs on your X86_64 cpu or whatever cpu you think you have. Firmware runs on the cpu in your nic or gpu or whatever. Different instruction set.

Yes but so is C++ distinct from Assembly. Having spent a little time in Assembly doing direct to disc writes and altering "firmware" of GPUs and Motherboards back in DOS days. I know what you mean... but there's nothing especially "firm" about that software. It just is a bit more out-of-sight, out-of-mind, for most folks. That's perception, not reality.

The BIOS/UEFI runs on the cpu and that's considered firmware. The kernel puts all that stuff in /sys/firmware. Anyway with modern SoC's, there isn't such a distinction any more.