Carbon Copy Cloner (free trial, highly recommended) or SuperDuper! (free version available).
You now have a portable, bootable Mac environment. Whether you’re testing a new OS, running legacy software, or simply keeping a disaster recovery tool in your bag, this setup puts you in control.
sudo /Applications/Install\ macOS\ Sonoma.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume (Change “Sonoma” to “Ventura” or “Monterey” as needed)
sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume