I am creating this topic as a continuation of the bug issue - https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=278984
Hi.
If you install Debian 12 on bhyve from an iso image in UEFI mode, you will notice that the grub boot loader will not be found.
To fix this you need to do the following:
mkdir /boot/efi/EFI/BOOT/
# copy file - workaround for bhyve grub package #
# Pay attention to destination file bootx64.efi #
cp /boot/efi/EFI/debian/grubx64.efi /boot/efi/EFI/BOOT/bootx64.efi
Taken here: https://www.cyberciti.biz/faq/how-to-install-linux-vm-on-freebsd-using-bhyve-and-zfs/
I suggest fixing bhyve so that it tries to load not only /boot/efi/EFI/BOOT/bootx64.efi, but also /boot/efi/EFI/debian/grubx64.efi.