will an installation destroy my grub?

[T-Daemon]

I tried that. I get an error: File `efi' not found.

My mistake. I haven't dealt with grub quite a while and had an alternative solution in mind which involves gpt3. I overlooked set root refers to where the boot loader is situated, not system root (necessarily).

Also I need my eyes checked. Seriously, it's in front, but I haven't seen it:

ls (hd1,gpt1)/efi/boot
BOOTx64.efi startup.nsh

Try setting for chainloader uppercase BOOTx64.efi:

menuentry "FreeBSD" { 
     set root=(hd1,gpt1)
     chainloader /efi/boot/BOOTx64.efi
}

You can also try this one:

menuentry "FreeBSD 12.1-RELEASE" {
       insmod zfs
       search --set --label zroot --hint hd1,gpt3
       kfreebsd /ROOT/default/@/boot/zfsloader
}

 

[kagi3624]

The first one just immediately throws me back into the grub menu to the Ubuntu choice and the second one my monitors just go blank. I guess I will try to install freeBSD on my other drive and if it does not work there I guess I have to live with it.

 

[T-Daemon]

I guess I will try to install freeBSD on my other drive and if it does not work there I guess I have to live with it.

You could also boot FreeBSD from the UEFI boot selection menu (F11) until found a solution for GRUB.