Hey Alan!

 AI> Please do.

The archlinux howto - a very worthwhile read - can be had at;

  https://wiki.archlinux.org/title/Unified_Extensible_Firmware_Interface

The commands below are from the perspective of a chrooted nvme disk from a sata boot.  The opposite will also apply to a properly partitioned and formatted sata disk chrooted to from a booted nvme disk.  Having two differing disks is what makes this idea even better.

 --- ye olde cut and paste starts ---
mkfs.vfat /dev/nvme0n1p1
install -dv /boot/{efi,grub}
mount -v -t vfat /dev/nvme0n1p1 /boot/efi

grub-install --bootloader-id=ZNVER2_NVME --recheck

cat > /etc/default/grub << "EOF"
GRUB_DISABLE_LINUX_UUID=true
GRUB_DISABLE_LINUX_PARTUUID=false
GRUB_GFXMODE=3840x2160x32,2560x1440x32,1920x1080x32,1280x800x32,1024x768x32,800x600x32,auto
GRUB_GFXPAYLOAD_LINUX=keep
GRUB_TERMINAL_OUTPUT="gfxterm"
EOF

grub-mkconfig -o /boot/grub/grub.cfg
 --- ye olde cut and paste ends ---

I REALLY need to get my grubby act together but the above does work on 3 machines here (not the BBS) which is an older machine without a proper m.2 socket for nvme disks.

 AI> I just booted AlienBOB's slackware64-15.0-livecd to practice my
 AI> make-foo a bit on the laptop before I move to the BBS machine.

Excellent idea.  However I believe he is using syslinux to kick start the live system.  It definetly worked here but I never tested it on the BBS which is a bios based grub.cfg.

 AI> I got penguins (4 of them) there.

Note the four ascii penguins below.  Same with the laptop and the EuroPoint which are both uefi.

Life is good,
Maurice

 o-   o-  -o   -o
/)   /)    (\   (\
^^   ^^    ^^   ^^
... Tungol sceal on heofenum beorhte scinan swa him bebead meotud.
    A star in the heavens must shine brightly, as the Lord ordered it.
--- GNU bash, version 5.2.15(1)-release (x86_64-pc-linux-gnu)