(Just to add a quick corrigendum here - you need to separately invoke #'package-install-selected-packages, after #'package-initialize and adding your ELPA repos

(Just to add a quick corrigendum here - you need to separately invoke #'package-install-selected-packages, after #'package-initialize and adding your ELPA repos, to install missing packages. Sorry for the error! It had been a few years since I needed to set up Emacs on a fresh machine, until last weekend when I did so and discovered the omission.)