Thank you for the info, for now I'll keep it as-is until I can find out how to properly do it. As a side note, the correct URL for the latest upload is https://mentors.debian.net/debian/pool/contrib/p/proton-caller/proton-caller_2.3.2-2.dsc I was lazy and just copied the last URL and changed the version number, forgetting the package is now in contrib.