This is exactly why anti-trust legislation needs to be extended to cover network effect platforms. A permanent ban from GitHub or LinkedIn has a non-negligible effect on career progression.
If there are competent employees that are not finding good jobs because they are not on GH/LI, then that is a market opportunity for people to start hiring people who explicitly don't have those things.
The idea being that since it was "economically irrational" to discriminate on the basis of skin color, the "free market" could therefore take care of it, therefore legislation was unnecessary.