Questions regarding configuration of systemd services on an Ubuntu server, do they belong on:
/questions/tagged/systemd after each link and compared volume of questions with that tag:
Results (as of writing):
- Server Fault - 834 questions
- Ask Ubuntu - 876 questions
- Stack Overflow - 1,268 questions
- Unix & Linux - 2,191 questions
Conclusion: I would say that Unix & Linux is the best place to post it, although the specifics of the question can affect where it will fit better.