BINGO – as I’m typing this I worked it out!
You have to be on the Blog page for the Blog section in Customizer to appear…
(for anyone else who has the same issue)
Hi just set up a brand new site to play with Elementor & I installed the add-ons, registered it, turned on all of then, but no Blog?
I turned them all off, just turned on the Blog – again no Blog.