So what if Github itself is not OSS? The technology behind is already open source and decentralized. You can switch to a Gitlab instance with just a few mouse clicks while also migrating your issues and pull requests.
I don't believe issues or pull requests are part of the Git repo. If there is a way to migrate them it would involve some GitHub API which could be shut down.
as much as many projects could use a clean slate here, i dont think the burden of migranting them manually or the act of just dumping them is realistic.
There are at least a few different "OSS scenes" that have different priorities. More principled, idealistic developers fall under a different category than more pragmatic ones, so it should be no surprise that they use different tools.
"Sharecropper programmers" might be an accurate way of describing developers for Apple platforms, but that's not what is happening when people use GitHub and Discord to work on open-source software. They can easily move their Git hosting and chat to another platform—they just choose to use the popular, coincidentally non-OSS, platform for its pragmatism.
A large base of existing users, easy onboarding, and good visibility makes a big difference for many OSS projects. Using a self-hosted Git hosting system and mailing list is a lot of work—and it adds a not-insignificant barrier to entry for potential contributors. What issues exist with popular, proprietary Git and chat tools that make them unsuitable for OSS development?
What are some of the considerations you're thinking of where using a popular option is not pragmatic?
It is a thing, is there enough of this thing? Is it free? Do these hosted services provide the infra and protection? Do these hosted services solve the issue of the dearth of clients for these services?
And if you look at hosted services like IRCCloud, it turns out they are not that different from Slack/Discord: closed source, for full range of capabilities you need to use their apps.