edk2-platforms VS efifs

Almost certainly the former as the latter is barely usable (if not outright unusable). Ampere says the Altra and Altra Max are compliant with Arm SBSA and SBBR, so compliant OSes that support UEFI and ACPI should just work (no need for SoC-specific kernel trees/etc like you tend to find on SBCs with lower-end SoCs). The devkit product page also mentions that it uses "open source EDKII" firmware. It looks like Ampere released the source code for their EDK II port and is working on upstreaming it. They also published a guide on how to build the firmware.

There's an rpi3/4 edk2 uefi firmware you'd have to use in order to run it, but it does exist

It's not entirely open source (it still depends on the FSP binaries), but Intel has released UEFI initialization code for older platforms. They also contribute platform support to coreboot (though this also depends on the FSP).

If you prefer building it yourself: https://github.com/tianocore/edk2-platforms/tree/master/Platform/RaspberryPi/RPi4

> They prefer to keep inner workings secret

https://github.com/tianocore/edk2-platforms/tree/master/Sili...

See also UEFI drivers that can read a bunch of other file systems (btrfs, ext2/3/4, HFS, ISO, NTFS, UFS/FFS, XFS, ZFS, etc):

* https://efi.akeo.ie

* https://github.com/pbatard/efifs

The UEFI spec specifies (§13.3) that firmware is only required to read FAT32/16/12, which is generally why your /boot/efi is VFAT/FAT32.

In theory you would still need a FAT32 efi 'stub' partition with the exFAT filesystem drivers which you have to load before loading the WinPE loader (bootmgfw.efi).

I am pretty sure that that I am doing something incorrectly with the configuration files for the rEFInd bootloader, but everything else should be correct. However, as I write this, I barely realized did I not use the following commands recommended from the "Usage" section from the aforementioned website where I downloaded the zfs_x64.efi driver file for rEFInd:

I found the drivers here https://efi.akeo.ie/ . Which means, that any EFI bootloader able to load them will be able to use them. They are not for bootloader, but it is the firmware which will use them. As i said, i am little bit afraid that it will not work on any board as some manufacturers have pretty buggy firmware when talking about infrequently used features. Also i am bit unsure they will work with secure boot as they are gpl3 thus will be never signed by Microsoft and i don't know what UEFI requirements for drivers are in this regard.

Even for those using systemd-boot with custom efi drivers to provide functionality, it's worth noting that those drivers are being developed downstream of GRUB.

I think you can also add btrfs filesystem support for sd-boot by including the EFI drivers for it on the EFI partition instead, from https://github.com/pbatard/efifs/releases I think. Haven't tried it myself though.

EFI doesn't actually mandate FAT for the system partition. The system partition can be any filesystem that the firmware supports.

Of course, pretty much all EFI implementations only support FAT, so it's a bit of a moot point; the only one I'm aware of that supports anything else is the one on Intel Macs, which also understands HFS+.

You can find a huge selection of EFI filesystem drivers at https://efi.akeo.ie/ but they're derived from GRUB and hence GPL, so don't expect the likes of American Megatrends to be bundling these any time soon.