There should be a faster way to list the supported boards with custom versions of U-Boot.
>From manual: Many ARM boards require a specific variant of the U-Boot (https://www.denx.de/wiki/U-Boot/) bootloader. If you build a disk image and the bootloader is not available otherwise (on another boot drive etc), it’s advisable to build an image that includes the bootloader, specifically: guix system disk-image --system=armhf-linux -e '((@ (gnu system install) os-with-u-boot) (@ (gnu system install) installation-os) "A20- OLinuXino-Lime2")' ‘A20-OLinuXino-Lime2’ is the name of the board. If you specify an invalid board, a list of possible boards will be printed. I think an example of an invalid board is "dne-board", which (last I checked) does not exist and probably never will exist. If I run the following command: guix system disk-image --system=armhf-linux -e '((@ (gnu system install) os-with-u-boot) (@ (gnu system install) installation-os) "dne- board")' guix tries to build an entire system. It doesn't look like it checks if "dne-board" is a valid board until it is building the image. It takes hours to cross-compile the kernel, and even longer if the kernel needs to be deblobbed. I have not yet been able to cross-compile any system using this method.