UEFI & Apple EFI
 

Since latest slackware current began to support UEFI, I am wondering whether it supports Apple EFI (instead of bootcamp BIOS)?

You might be able to mount the USB installer image under /mnt and bless the bootloader under MacOS like this:

You'd also need to bless the elilo that you install when setting up the installed partition to be bootable. No Mac here for testing, but this is my understanding. There's no plan to make the DVD bootable by a Mac at this time, though. That would require an additional HFS+ El-Torito image. I'm also not clear about whether the FAT USB installer image will work directly, or if it would need to be copied to an HFS+ partition in order to work (I suspect this is the case, though).

Thanks for the hints. I tried the "sudo bless --setBoot --folder /somelocalfolder/EFI/BOOT --file /somelocalfolder/EFI/BOOT/BOOTX64.EFI", and I was able to boot into slackware install prompt screen by long pressing Option key and then selecting efi boot from the screen. But ELILO boot: could not find a kernel to boot. What need to be done further?

Assuming the rest of the files are also in /somelocalfolder (since the initrd and kernel aren't in /EFI/BOOT), probably you need to adjust the paths in elilo.conf to point to where they are, e.g.:

image=/somelocalfolder/huge.s
initrd=/somelocalfolder/initrd.gz

Thanks for your great support. Your approach works great. I did not expect that it is so easy now for mac machines.