The alternative to GitHub is already here. It is called self-hosting and there are many alternatives.
The Linux kernel is not hosted on GitHub and uses cgit. Others use GitLab, or Gitea and there is also Forgejo (Which Codeberg uses) that people are using and can be self hosted.
This is why now everyone is realising why "centralising everything to GitHub" [0] was a terrible idea and now GitHub has been (unsurprisingly) run into the ground.
As a casual user, I find the UI incredibly confusing. And not just because it's different from GitHub, but because there are so many features and there are menus absolutely everywhere.
I'm sure if I used it more often that I would figure it out, but it's deeply off-putting for someone who only uses it twice a year or so.
The Linux kernel is not hosted on GitHub and uses cgit. Others use GitLab, or Gitea and there is also Forgejo (Which Codeberg uses) that people are using and can be self hosted.
This is why now everyone is realising why "centralising everything to GitHub" [0] was a terrible idea and now GitHub has been (unsurprisingly) run into the ground.
[0] https://news.ycombinator.com/item?id=22867803