Just signed up to the site with using GitHub and set my profile picture (manually) to my GitHub one. I thought there’d probably be a way for this to happen automatically, and indeed such a feature was added to Discourse in 2017 (github .com/discourse/discourse/pull/5073). (Can’t post with the link for some reason?)
I don’t know how easy this would be to enable but it would be pretty convenient to have.
Thanks