Top 3 Alternative (Similar) to Azure DevOps Server

Enterprise · A smarter way to work together · GitHub. Whether you’re working solo or leading an enterprise, GitHub has everything you need to build and scale your team’s workflow.

GitHub Enterprise is the on-premises version of GitHub.com. GitHub Enterprise includes the same great set of features as GitHub.com but is packaged for running on your organization's local network.

Bitbucket Server and Data Center | Bitbucket. Bitbucket is built for professional teams. Get full control of your source code with our self-hosted deployment options: Server and Data Center

GitLab for Enterprise - Collaboration made easy | GitLab. Accelerate Enterprise software delivery with GitLab’s DevOps platform, lowering your development costs and streamlining team collaboration

Gitlab offers four different versions of the self-hosted Revision Control System or Code Management system, starting with a community-supported free version. The paid version has business support from Gitlab and offers features like Issue Boards, Time tracking, GitLab Releases, etc...