theChiChen has created a new Github project with some hello-world-level UEFI applications. Besides a few Hello Worlds, there is are Stall and ResetSystem commands. These are built with EDK-II/Tianocore, not GNU-EFI toolchain.
One of these days, I need to create a list of all these hello-world apps for UEFI and other firmware targets. There used to be only a handful, now there’s a few dozen..