Like what?

• OCI registry? GitLab.
• pull request model? Every one of the competing services
• CI/CD system based on YAML definitions? Most every competitor.
• static site hosting? Most competitors
• protected branches? Most competitors

I’m not saying there isn’t vendor lock-in, but I am saying it likely isn’t the features of GitHub that are limiting that. Third party integrations will follow wherever the foot traffic goes.

• direnv
• nixpkgs (with flakes enabled)
• committed flake.nix and flake.lock
• Makefile or several shell scripts in bin/ for common tasks

(explainer)