I see your point, and I don't use GH when I can avoid it, but those are very different in my mind. GH, for all its flaws, is a value-added hosting service on top of git. It interoperates freely with any other Git host and you can clone/pull at any time. Discord is in an entirely different category: a completely proprietary reimplementation of IRC, with rent-seeking features bolted on.

For issue management, sure – but just using Github doesn't remove the semi-decentralization of git.

A friend and I recently started a dev collective (https://pico.sh) to work on projects targeting the smol web. We decided that many popular communication and collaboration tools would not fit into our stack. Things like GitHub and discord were out of the question pretty quickly.

Instead we opted for Sourcehut and irc and have been pretty happy with the results.

At least some of the things on GitHub are not inside a walled garden.