> I think you’ve got it backwards. GitHub is by far the market leader for hosted repositories

Maybe, but I never heard about any company using github for internal projects in my real life. For me it was always to go to for open source projects.

Then again it's not a topic that often comes up in my developer circles.

More than half the companies I have worked for use Github. The others used Atlassian tools which were at least as bad from a reliability perspective and much less nice to use (IMO).