Luhmann's 1968 two-pager is briefly mentioned in an essay "Zettels Albtraum" by Johannes Schmidt: https://www.wiko-berlin.de/fileadmin/Dateien_Redakteure/pdf/ZIG/2023_3/ZIG_2023_3_red.pdf, see page 5/6.

"Sankt Niklas" is the focus of that issue, with an introduction and 11 essays dedicated to Luhmann.