the pervious tech had shoddy coverage and was bound to eventually break
because of the rise of /etc/os-release to rule all the proprietary release
files that preceded it.
instead we now set sane default assumptions and attempt to load the actual
default for the specific system from /etc/login.defs (part of shadow source
and should be available on more or less all modern linux systems
https://github.com/shadow-maint/shadow).