This has also broken a bunch of packages in the arch user repository, for example https://aur.archlinux.org/packages/dendrite/ :(
This sounds for the better. Not having code mirrors (as other distribution channels) sounds not just insecure, but borderly malicious.
If a project is using github to publish releases, where else are consumers of that software going to get them from?
Having all sources of everything that is packaged backed up is a must for the official repository of a competent distro, but even in that case there is no reason not to use github in normal operation.