I've been following their move to on premise with interest and this was a great read. I'm curious how they are wiring up GitHub actions with their on premise deployment. How are they doing this?

The best I can think of for my own project is to run one of the self hosted GitHub actions runners on the same machine which could then run an action to trigger running the latest docker image.

Without something like that you miss the nice instant push model cloud gives you and you have to use the pull model of polling some service regularly for newer versions.