Are there completely self-sufficient autotrophs? Are there completely self-sufficient autotrophs which can survive and reproduce indefinitely by consuming exclusively non-organic matter (plus energy from sunlight or thermal vents etc.)? I'm asking specifically.

It really depends on what you mean by "organic matter". No cell is going to be able to grow and reproduce without an appropriate source of CHON atoms (plus lesser amounts of the other necessary elements).

So, if by organic matter you mean CHON+, then no, everything needs organic matter to grow and reproduce.

If by organic matter, however, you mean natural organic materials like soil or groundwater, then yes, there are lots of things that can live on chemical mixtures that can be produced by purely synthetic means. A simple example is M9 media, which is a commonly used bacterial culture medium.