Expanding on Frankston's answer (i.e. commentary that is too long to format as a comment):
I've always considered lilypond to be directly on topic for Musical Practice & Performance, given the indication that "usage of specific music software" is on topic.
I'm certain that there are many users who are experience in how to read lay-out music notation in general, and there are a few who are using lilypond specifically.
I can see an argument that more complicated lilypond scripting, i.e. once users start to
program in guile within their lilypond files, could be more of a Superuser or Stack Overflow type of question.
However, to date it looks like all of the questions are "how do I get lilypond to output what I want" (Music Practice) rather than "how do I do complicated programming within a lilypond file" (SuperUser),
so I'd still say that the primary location for basic lilypond usage questions is Musical Practice & Performance.
As a final note, prompted by PeterBjuhr comments/answer, one of the reasons why there are so few questions is because lilypond has an active and helpful mailing list; and you're likely to get better answers there (at least for now).