Coreboot has some pretty solid ARM support too. Modern Chromebooks (both x86 and ARM) use Coreboot with a "depthcharge" payload. You can even use Libreboot at this point to bring up an RK3288, and boot into ChromeOS or a traditional linux. Even cooler is that if you do your own build of Coreboot, you can provide your own OS verification keys, and use vbutil to sign your own OS and have custom verified boot.

>> Coreboot is also very x86 centric last I checked.

Actually RISC-V is fully supported:

https://riscv.org/wp-content/uploads/2016/01/Tues1345-riscvc...

Real hardware coming soon...

Isn't UEFI way more complex? But I'm not sure if that's a problem because of Windows and all the drivers it has to support, or if it's a problem with the specification. I believe it was the latter? I think Google mentioned that in its recent talk on removing Intel ME.

UEFI is more complex but also nicer for management.

Developing a runtime on UEFI is easy to setup and get going, you don't have that feature in coreboot.