While I don't use GitHub for personal projects, I don't see how moving off GitHub solves anything. If you are open source contributor, then repositories you interact with are public, and there is nothing preventing anybody (including GitHub) from using your code for any purpose. If you contribute to a public repository on any public platform, be it Codeberg, sourcehut or GitLab, your activity is public, issue you create are public[1], everybody knows who changed what in the code.

The social media effects are twofold, on one hand I think stars and contributors count, contributor profiles are great to see what is popular, but it went a little too far when they added scrollable home page. Virtually everyone has an account on GitHub, the best way to make your project visible and ease the contribution threshold is to put your project on GitHub.

What I would like to see is federated git, so that some protocol allowed different git servers could communicate with each other, which will make moving off GitHub much easier.

[1]: except for sourcehut I guess, which does not have issues or pull requests?

https://forgefed.org/