I'm having issues with the kernel loading when trying to multiboot. I had previously fixed a similar issue but following a fresh Kali install (and it's attendant automatic reinstall of grub) I've screwed it up again and can't remember how I fixed it a couple of years ago.
Currently I'm running Fedora 29 as my driver (upgraded internally from 27), a fresh install of rolling 19 Kali, and Windows 10. Each of the OSes are recognised as a seperate device in the BIOS device manager, and the Linuxes are configured to see the EFI partition. If I select either Kali or Fedora from either the BIOS or the boot menu on startup, I can sucessfully via grub boot that OS and all that OS's recovery options as well as Windows, but it will not boot the other Linux or any of its recovery options. I get different errors from both, but it seems to basically amount to a kernel error. Fedora dumps me into Emergency Mode with a commandline, and on further investigation spits out a problem about reading EFI partition because it cannot load a vfat module, while Kali just tells me to load the kernel first before spitting me back to its grub bootloader. Refreshing the grub.cfg in either install (via update-grub or grub2-mkconfig) makes no difference.
It's not a deal breaker, all three OSes are bootable, but I'd like to be able to boot all from one place rather than having to go down the separate branches to get to each. Any advice would be appreciate, I'm sure I've just done something dumb :P I think I currently have CSM turned off in the BIOS, turning it on makes no difference to the above.