@argiris So what I observe is a mix of them:
Basically waterfall but with shorter cycles.
When I am interviewing companies (because looking for employment) I'm asking on how they set up their process.
You can be lucky if you find disciplines outside of development and support.
Designers are shared among teams. QA is done by interns or students. Devs are responsible for Ops.
The waterfall aspect here is this: