What is the proper way to boot Debian 12 Install CB from GRUB? Can't detect install Media

Question

I need to set up Debian 12 on a remote system and can only access the install media through GRUB. I can boot the image, but it can't find the install media. My /etc/grub.d/40_custom entry is as follows:

menuentry 'Debian Install Image' {
    insmod part_msdos
    insmod ext2
    set root='(hd0,1)'
    set isofile='/images/debian-12.6.0-amd64-DVD-1.iso'
    set initrdfile='/images/debian-12.6.0-amd64-DVD-1.gz'
    loopback loop (hd0,1)$isofile
    linux (loop)/install.amd/vmlinuz findiso=$isofile iso-scan/filename=$isofile priority=low noeject
    initrd $initrdfile
}

The initrd was copied from the ISO's /install.amd/initrd.gz

The same method was used almost verbatim on a Debian 10 system and works great. Any advice for helping it to find the install media?

EDITS: I want to clarify, it's the Debian install media I want to try and use, not a live CD. It appears that the Debian 12 installer media initrds don't actually have the filesystem (ext2, etc) modules needed to be able to read an iso install media from a hard drive any more. I was incredulous at first, but it seems this is actually the case. This leaves me without being able to use installer media with the packages already included.

Answer 1

I am using Kubuntu so I downloaded Debian live kde.

I have a data partition (hd1,5) with an /ISO folder, so that is my path. Parts of entry from older gparted ISO boot and from grub inside ISO. This entry is actually in my livecdimage.cfg in my /ISO folder.

    menuentry "Debian Live system (amd64)" --hotkey=l {
        insmod part_gpt
        set isofile="/ISO/debian-live-12.5.0-amd64-kde.iso"
        loopback loop (hd1,5)$isofile
        linux (loop)/live/vmlinuz-6.1.0-18-amd64 boot=live config union=overlay username=user noswap noprompt ip=frommedia findiso=$isofile toram=filesystem.squashfs
        initrd (loop)/live/initrd.img-6.1.0-18-amd64
    }

Just rebooted and booted the live ISO with above boot stanza. I have many ISO in my /ISO folder. I prefer to create one entry in grub's 40_custom as a configfile to a grub/text file (livecdimage.cfg) in my /ISO folder. Example of boot stanza added to 40_custom.

    menuentry 'Live ISOs in nvme_data drive' {
    search --set=root --label nvme_data
    configfile /ISO/livecdimage.cfg
    }
    # spacer line
    menuentry " " {
    set root=
    }
    
    menuentry "System restart" {
    echo "System rebooting..."
    insmod reboot
    reboot
    }
    
    menuentry "System shutdown" {
          echo "System shutting down..."
          insmod halt
          halt
    }

The livecdimage.cfg is just a text file with grub boot stanza. That way I do not have to remember to update grub with changes to 40_custom as I just edit livecdimage.cfg with new ISO boot stanzas.