a Spack extension to find external/system pacakges using linux package management tools; this finds many more packages than the current spack external find' This generates an updated packages.yaml file in the requested scope.
In most cases you can just do:
spack linuxexternals
but you can specify --scope scope-name to specify where the packages.yaml will be generated.
After cloning the repository somewhere, See the Spack docs on adding the path to config.yaml under 'extensions:'