I know it's not germane to this but the boot is also successful with the GRUB_GFXPAYLOAD_LINUX=text line commented out in /etc/default/grub (I did run update-grub)
I know it's not germane to this but the boot is also successful with the GRUB_GFXPAYLOAD _LINUX= text line commented out in /etc/default/grub (I did run update-grub)