What open-source tools are best for DevSecOps learning?

What open-source tools are best for DevSecOps learning, especially for students and beginners aiming to build real-world skills? I am looking for tools that cover the full DevSecOps lifecycle, including CI/CD integration, code scanning, container security, infrastructure as code, and cloud security. Which open-source tools are most commonly used in the industry and suitable for hands-on practice at home? Also, how should beginners combine these tools into a practical learning roadmap without getting overwhelmed? Any recommendations for labs, projects, or pipelines that align well with DevSecOps Training programs would be highly appreciated. Insights from professionals or learners are welcome.