hello jonh i'm manuel one of the Peppermint developers responsible for
building the 32 bit isos for both Devuan and Debian.
I think I can help you with your project.
But first I'll give you an explanation of how the isos are built.
as the isos are built using a debian server some changes will have to be
made in the live-build tools mainly in the debootsatrap package added the
settings for it to work with Devuan which are the following

replacing the symlink ceres in usr/share/debootstrap/scripts/ with a text
file of the same name with the following content

mirror_style release
download_style apt
finddebs_style from-indices
variants - buildd fakechroot minbase
keyring /usr/share/keyrings/devuan-archive-keyring.gpg

include common settings
if [ -e "$DEBOOTSTRAP_DIR/scripts/debian-common" ]; then
🇧🇷 "$DEBOOTSTRAP_DIR/scripts/debian-common"
elif [ -e /debootstrap/debian-common ]; then
🇧🇷 /debootstrap/debian-common
elif [ -e "$DEBOOTSTRAP_DIR/debian-common" ]; then
🇧🇷 "$DEBOOTSTRAP_DIR/debian-common"
else
error 1 NOCOMMON "File not found: debian-common"
fi

and then create a symlink for that file with the name chimaera

and then the keyring of Devuan and debian systems will have to be installed
if it is Devuan it is not necessary

both files are located in
usr/share/debootstrap/scripts/

The other change needed was to the live-build package in
/usr/share/live/build/data/debian-cd

creating a symlink for the squeeze folder with the name chimaera

after these changes the isos will start to be built.
using the Debian live-build and the calamares-settings-debian package with
some tweaks to the module settings that you are sure you already know
everything works fine.

you can consult the peppermint repositories on codeberg and also mine also
on codeberg mainly this one

https://codeberg.org/manuelr1/My-distro-configs-devuan

hope i helped take care
until one next
I will always be available if you need help


these are some
screenshots from one of my personal projects