The last time i tried to get pi running with a distro that wasn't raspbian it was huge PITA, with having to use custom kernel patches and weird proprietary firmware and annoying boot process, am I misremebering or did this change ?

On any x86 UEFI system I tried i never had any issues at all, but Pi's I remember as a huge PITA...

Or is this just a general ARM issue ?

> Or is this just a general ARM issue ?

I understand that this is the case. IBM did the PC world a solid by not encumbering the original H/W. That provided a basis for a platform that could be copied and provide a "standard" that others could leverage, including copying and reverse engineering the BIOS that launched the OS. That provided the foundation of the PC explosion. They tried to reverse their "mistake" with the Microchannel Architecture and that saw limited success (AKA failed.)

IBM was also part of a consortium that tried to develop a common platform for the Power architecture. I'm not sure if any of that survives in their current offerings but it did not take anything away from the Intel (Windows) market and except for Apple, the Power PC was nowhere to be seen.

ARM processors have proliferated in the hand held (phone, tablet) market where volumes are sufficient for the manufacturers to provide their own solution to bootstrapping the OS. There are some efforts to agree on a common boot architecture (Yocto, UEFI and probably others) and I'm not familiar with them, but I hope one succeeds so we can easily load a variety of OSs on our devices.

Incidentally... The GPU in the Raspberry Pi performs the initial stages of the boot process. Weird. I think that Pi 4/5 generations are moving away from that but I'm not familiar with the detains. As near as I can tell, they've preserved the S/W structure required for the GPU to perform this function.