Looks good to me, great work!

Please add some documentation on what the new build options are and what they do, e.g., as a longer Doxygen docstring.

It would also be good to give examples of the possible configuration options in the SCION example. I'd add a paragraph to the README in examples/S01_scion.

I was not able to replicate the issue @martenwallewein was facing, but I only tried the default build configuration.

Reviewed 3 of 3 files at r1, all commit messages.
Reviewable status: all files reviewed, 7 unresolved discussions (waiting on @divinepaul and @martenwallewein)

seedemu/layers/ScionRouting.py line 108 at r1 (raw file):

    def __install_scion(self, emulator: Emulator, node: Node):
        """Install SCION packages on the node."""

Please change the comment as well, as the method is no longer installing SCION from the ETH packages.

seedemu/layers/Scion.py line 130 at r1 (raw file):

        try:
            result = urlparse(url)
            return result.scheme in ("http", "https") and bool(result.netloc)

Casting to bool looks kind of ugly to me. Maybe do a is not None'or != ""check instead. Whichever is actually intended.

seedemu/layers/Scion.py line 141 at r1 (raw file):

        # Ensure the URL ends with .git for Git repositories
        if not url.endswith(".git"):
            raise ValueError("URL does not look like a Git repository (missing .git)")

Requiring the URL to end in .git seems overly restrictive. Git repos don't have to end in .git. I'd remove the check.

seedemu/layers/Scion.py line 182 at r1 (raw file):

    def generateBuild(self) -> str :
        """
        method to build all scion binaries and ouput to .scion_build_output based on the configuration mode

ouput -> output

seedemu/layers/Scion.py line 246 at r1 (raw file):

        self.__links = {}
        self.__ix_links = {}
        self.__default_build_config = ScionBuildConfig()

I'd pass the build config in as keyword args for the Scion layer constructor instead of using a separate method.

seedemu/layers/Scion.py line 252 at r1 (raw file):

        return "Scion"

    def getBuildConfiguration(self) -> ScionBuildConfig:

There is an asymmetry between setBuildConfiguration and getBuildConfiguration. The getter is returning a different type the the setter is setting.
Should getBuildConfiguration even by a public method? Only the ScionRouting layer is calling it, and only to call generateBuild() on the build config. Maybe make generateBuild a method on the SCION layer?

seedemu/layers/Scion.py line 255 at r1 (raw file):

        return self.__default_build_config

    def setBuildConfiguration(self, buildConfig: Dict[str,str]):

Keyword arguments would be more Pythonic than passing a dict. Make the signature setBuildConfiguration(**buildConfig). Or move to constructor as noted above.