How to make an El Capitan usb bootable disk from an M1 Mac

El Capitan Disk maker for M1 Mac

# verbatim copied over from - https://apple.stackexchange.com/a/420325

# Download install DMG for El Capitan
# https://support.apple.com/en-us/HT211683

wget -c http://updates-http.cdn-apple.com/2019/cert/061-41424-20191024-218af9ec-cf50-4516-9011-228c78eda3d2/InstallMacOSX.dmg 

# mount and unzip the packager

pkgutil --expand InstallMacOSX.pkg Installer
cd Installer/InstallMacOSX.pkg
tar -tvf Payload
tar -xvf Payload
cd ../../
ls

# start making a disk
mkdir dmg
cd dmg

cp ../Installer/InstallMacOSX.pkg/InstallESD.dmg .
hdiutil attach InstallESD.dmg -noverify -nobrowse -mountpoint /Volumes/install_app
hdiutil convert /Volumes/install_app/BaseSystem.dmg -format UDSP -o /tmp/Installer
hdiutil resize -size 8g /tmp/Installer.sparseimage
hdiutil attach /tmp/Installer.sparseimage -noverify -nobrowse -mountpoint /Volumes/install_build
hdiutil attach /tmp/Installer.sparseimage -noverify -nobrowse -mountpoint /Volumes/install_build

# copy files over
rm -r /Volumes/install_build/System/Installation/Packages
cp -av /Volumes/install_app/Packages /Volumes/install_build/System/Installation/
cp -av /Volumes/install_app/BaseSystem.chunklist /Volumes/install_build
cp -av /Volumes/install_app/BaseSystem.dmg /Volumes/install_build
hdiutil detach /Volumes/install_app
hdiutil detach /Volumes/install_build

# resize to smallest possible

hdiutil resize -size `hdiutil resize -limits /tmp/Installer.sparseimage | tail -n 1 | awk '{print $ 1}' `b /tmp/Installer.sparseimage
hdiutil convert /tmp/Installer.sparseimage -format UDZO -o /tmp/Installer

# Got the disk in DMG form
cp /tmp/Installer.dmg ElCapitanInstaller.dmg

# flash onto USB drive (mine is a failed Monterey Install disk)
sudo asr restore --source ElCapitanInstaller.dmg --target /Volumes/Install\ macOS\ Monterey --noprompt --noverify --erase