What github should do is like what I said please login first (which is what most user perplexed when they click the UE4 github link - they found 404 error). And then when they login, they will find the repo. But if the repo doesn’t exist or inaccessible (private repo etc), then github can display 404 - it is good enough. No one mentioned about fixing the 404 error by returning a list of repo, even if they are private.