Playing a bit with my experimental RPI4 mageia-cauldron. Put it to work and compiled uboot-tools and it's odd dependencies (vboot-tools, arm-trusted-firmware) and a few uboot binaries,
among them the (Rockchip) rk3399 which needs a cross compiler because it has an (arm)cortex-m0 on board.
All went well (just a minor dependency name change glib-static > glib-satic-devel) which is nice because the rpi4 is preforming well,
this also means it wouldn't be to hard booting every SBC compatible with mainline-{uboot kernel}
As said before my preference goes out to let uboot load the grub2-efi stub, unfortunately the location where uboot looks for the stub is hard coded;
it would need a patch like this (1) specific for mageia.
My primary question is: can uboot be sure to find grub<arch>.efi in (/boot/EFI/)EFI/mageia/ ?
Do not find "shim" or any fallback xxx.efi on my x86_64 test vm
Secondary question: Is my assumption correct all it needs to porgess booting is loading the grub(2)-efi stub?
**EDIT** update url to proposed mageia specific patch
1) https://github.com/markVnl/rpms-uboot-tools/blob/wip_mga8/uefi-use-Mageia-specific-path-name.patch