Updating Slackware 15.0+

I just recently built a new PC whereupon I cannot enable CSM on my motherboard so I am trying to move an existing Slackware 15.0+ MBR image on hard drive to UEFI. I posted a thread on this forum back in February 2022, https://www.linuxquestions.org/quest...ub-4175708479/, that detailed directions to make this happen which I have summarized here:

Code:
To fix:
reimage the hardrive
boot ubuntu usb,
use gparted to shrink sda1 and create a 200mb fat32 partition flagged esp.
open a terminal

to convert to gpt drive use gdisk

sudo gdisk /dev/sda

after converting to gpt mount /dev/sda1 and chroot into the system and install grub
chroot /mnt /bin/bash

sudo mount /dev/sda1 /mnt
sudo mount --bind /dev /mnt/dev
sudo mount --bind /proc /mnt/proc
sudo mount --bind /sys /mnt/sys
sudo mount --bind /run /mnt/run
sudo chroot /mnt
mkdir /boot/efi
mount /dev/sda2 /boot/efi
grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=grub
grub-mkconfig -o /boot/grub/grub.cfg
exit

Also if used in a virtual environment:

mkdir /boot/efi/EFI/boot
cp /boot/efi/EFI/grub/grubx64.efi /boot/efi/EFI/boot/bootx64efiAll these steps worked great and I was able to have a UEFI bootable Slackware platform on my new PC then. I tried with basically the same hardware today on a new machine...same exact motherboard, same RAM, and same processor. This is the error message I get when I try the grub-install today.

Code:
bash-5.2# grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=grub
Installing for x86_64-efi platform.
EFI variables are not supported on this system.
EFI variables are not supported on this system.
grub-install: error: efibootmgr failed to register the boot entry: No such file or directory.Repartitioning the hard drive and converting to a GPT drive worked ( on /dev/sda -- sdb is the usb drive I am using to make these modifications).

Code:
root@robby-Z690-UD-DDR4:~# parted -l
Model: ATA Samsung SSD 870 (scsi)
Disk /dev/sda: 1000GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number Start End Size File system Name Flags
1 32.3kB 999GB 999GB ext4 Linux filesystem
2 999GB 999GB 537MB fat32 EFI system partition boot, esp

Model: USB SanDisk 3.2Gen1 (scsi)
Disk /dev/sdb: 61.5GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number Start End Size File system Name Flags
1 1049kB 538MB 537MB fat32 EFI System Partition boot, esp
2 538MB 61.5GB 61.0GB ext4

root@robby-Z690-UD-DDR4:~# gdisk /dev/sda

GPT fdisk (gdisk) version 1.0.8

Partition table scan:
MBR: protective
BSD: not present
APM: not present
GPT: present

Found valid GPT with protective MBR; using GPT.
I do see that efivar must be installed:

Code:
bash-5.2# efivar --usage
Usage: efivar [OPTION...]
-t, --attributes=<attributes> attributes to use on append
-l, --list list current variables
-p, --print print variable specified by --name
-D, --dmpstore use DMPSTORE format when exporting
-d, --print-decimal print variable in decimal values specified
by --name
-n, --name=<guid-name> variable to manipulate, in the form
8be4df61-93ca-11d2-aa0d-00e098032b8c-Boot0000
-a, --append append to variable specified by --name
-f, --datafile=<file> load or save variable contents from <file>
-e, --export=<file> export variable to <file>
-i, --import=<file> import variable from <file
-L, --list-guids show internal guid list
-w, --write write to variable specified by --name

Help options:
-?, --help Show this help message
--usage Display brief usage messagebut when listing the variables, which I can do on the working UEFI machine lists nothing.

Code:
bash-5.2# efivar --list
efivar: error listing variables: Function not implementedHas something changed with Slackware since 2022 that needs to be modified to make this work now?

Thanks for any help.