The macOS bit wasn’t about trying to get systemd logs on mac. The issue was that the build itself fails because libsystemd-dev isn’t available. We (naively) expected journal support to be something that we can detect and handle at runtime.

Well... yeah. It's a Linux API for a Linux feature only available on Linux systems. If you use a platform-specific API on a multiplatform project, the portability work falls on you. Do you expect to be able to run your Swift UI on Windows? Same thing!