SLP is still in factory and according to the package maintainer continues to be maintained there. I think the config can stay, no harm?

It harms:
https://en.opensuse.org/openSUSE:Packaging_UsrEtc
https://github.com/uapi-group/specifications/blob/main/specs/configuration_files_specification.md

And there is even a Jira for it:
https://jira.suse.com/browse/PED-240?jql=text%20~%20%22usretc%22