I would flag github as a more crucial requirement. We've had various im/irq platforms for decades. They weren't really a substitute for video - but video is only a tiny fraction of team communications, and simple chat satisfies most of those requirements.
You're thinking too small. A tiny fraction of the people in the US use GitHub. Even a relatively small fraction (certainly under 50%) can use Zoom to do their jobs.
Remote collaboration tools like GH have been crucial for remote work for software developers, but that's a really small slice of the pie.
Even at companies that employ software developers, many don't use GitHub specifically or don't use much. And most of the sales, marketing, finance people at those companies don't use GitHub much either. Many of the developers I know were collaborating on open source projects around the world before GitHub came along so it's hardly a prereq.
Instead of github you should say code repositories. We used subversion back in the earlier 2000s to do remote work with contractors. It worked just as good as GitHub for remote collaboration.
