I would far prefer that software projects assumed competence in the installers knowledge of their systems package manager and just listed the specifics... honestly how hard is it to just say "here is our $gpg key" "here is our $apt_repo_url" the package name is "$foobar". And let competent system admins take it from there. Most of the time you end up de-composing the scripts into ansible/$sys_automation_tool_of_the_week anyhow.