Comment # 6 on bug 1213788 from Olav Reinert

(In reply to Franck Bui from comment #4)
> If you put unit files in /usr/local you need to tag this directory to be
> mounted earlier in initrd as described in
> https://www.suse.com/releasenotes/x86_64/SUSE-SLES/15-SP2/index.
> html#systemsManagement.

Thank you for the tip, this solves the issue for me. As far as I am concerned,
this bug can be closed now.

> For some reasons this release note hasn't been forward ported to more recent
> versions of SLE, that's probably a bug.

If you wish, you can also keep this bug report open and repurpose it to track
the documentation bug.