Our customer has hundreds and thousands of applications, and 12 are part of my current project. Three of those applications are using GitHub as a code repository. The rest use Bitbucket. This customer is an Atlassian shop, so only I don't think more than 50 people use it.
Any code they develop will be version-controlled in this GitHub tool, and they use the branching and merging strategy to promote their code. We use it for version control and parallel development.
The code in GitHub will be consumed by CI/CD pipeline for the build and deployment. We're using the latest version, which has a feature called GitHub Actions that enables CI/CD within GitHub, but this organization doesn't use GitHub Actions. They prefer Bamboo.