Hi @ninermac,
Thanks for trying out this module!
Sorry about the confusion with usingit with composer, I had forgot to publish the package on packagist.org that is why you had difficulties to fetch it I guess. I fixed that and the module is now available:
About the authsources.php simplesamlphp configuration example, I added an concrete example in the README of the module:
I hope it helps, let me know if you managed to use it. Thanks!