Still no debugging HOWTO, much less (but still poorly documented) DEBUG-related environment variables?

If you want people to troubleshoot your stuff (which is arguably the #1 documentation to start with), gotta start someplace (which is for most of us is agrep'ing the code, or save yourself a step and look at my link).

Or the RedHat/IBM systemd development team can quit doing that terse but cryptic error code output.

Or the documentation team can start covering these error codes.

But having to do any form of "agrep" is a sign of poor ... everything, unless formenting job security is what the ultimate goal is.