Ahoy @IdentityCrisis ,
Also you can read this thread - it is a recent one with Grub2 present on the machine and Haiku booted with configuring the chainloader mode.
It needs to be familiar with bootloaders and partition stuffs at least on basic level - it is also good to know that 64 bit Haiku boot needs EFI boot, 32 bit Haiku uses BIOS boot loader basically.
Haiku images have both available in the images, but recommended to use this way to boot successfully.
I had no experiences 32bit uefi Haiku bootloader, and bootloader - in bios compat mode - had not loaded the 64 bit Haiku install for me.
In case grub it loads the Haiku bootloader, so in case
32bit you must chainload config the bios version bootloader
64bit you must chainload config the uefi version 64 bit bootloader
There’s a small ESP (standard FAT) partition in the installer image, you can find the EFI bootloader there, but you can find it in the installed BFS volume, as the mentioned Installer material describes where are resides in the installed Haiku BFS filesystem, or in the installer Haiku instance as well.