systemd unitfile verification fails while doing FAI installation

When installing debian/bullseye via the FAI infrastructure, FAI class LAST includes script 69-chef which calls among others sys::chef.rb. The resource systemd_unit fails to verify the unit. Calling systemd-analyze after FAI installation in shell following error message appears:

System has not been booted with systemd as init system (PID 1). Cant operate. Failed to connect to bus: Host is down