I don't think it should all be taken that literally. It's not about literally using GitHub or stackoverflow but about having anything demonstrable, even if it's

I don't think it should all be taken that literally. It's not about literally using GitHub or stackoverflow but about having anything demonstrable, even if it's just words on paper about what you did in your role and not a link to something public. If you can't show anything, you're a tough sell no matter where you apply, and that's not meant meanly but it's the problem literally everyone has when looking to get their first serious job without having done side projects or other demonstrable things in the past. You might be offered an entry level position if they don't simply take your word for it or have tests available to assess claimed skills. (On the other hand, a friend once took a test for a job, like hacking some application for a security consultant position, did very well at it, better apparently than someone who joined a month earlier and gets a principal consultant title and salary, but my friend was given a junior position... YMMV how much they care about tests if you can talk the talk and are of the age to get grey or bald.)