Yes, I appreciate that /etc/ is for site configs these days - but that’s a distinction, cf /usr/ for distro configs, that’s only relatively recent and still a work in progress which NM doesn’t yet seem to have caught up with because there is no provision for NetworkManager.conf under /usr/ in the manual - unless, SUSE has provided an exception for /usr/lib/NetworkManager/NetworkManager.conf in its NM, then that file is redundant, unless it’s for copying to /etc/NetworkManager/NetworkManager.conf.
Perhaps there’s a case for posting a bug upstream that /etc/NetworkManager/NetworkManager.conf should be moved to /usr/lib/NetworkManager/NetworkManager.conf?
I did not enter the whole conversation here (how interesting it may be), I only commented on naming configuration files in /etc as “User” configuration (being them in the “old style” where they where mostly the only config files of a (group of) program(s), or in the “new style” as drop-ins). Where, as commented, a user can not even change anything.
Often there is not enough understanding about the fact that Unix/Linux is a multi-user (and multi-session) operating system. E.g. saying “I did this”, does not explain much. The system does not know you, it does “know” users.
Another general comment. It seems that SUSE is following the manual where it says:
NetworkManager does not require any configuration in NetworkManager.conf. Depending on your use case, you may remove all files to restore the default configuration (factory reset). But note that your distribution or other packages may drop configuration snippets for NetworkManager, such that they are part of the factory default.
But, then /usr/lib/NetworkManager/NetworkManager.conf still seems redundant.