https://github.com/semaphoreio/semaphore

I am part of the team that open-sourced Semaphore. For more than 10 years, Semaphore was a cloud-only, managed CI/CD platform. As of today is open-source (Apache-2) and self-hostable. Semaphore is SOC2 Compliant.

We open sourced Semaphore because we know not everyone likes or can use a managed service. And we found existing open-source CI tools too complex to setup and difficult to use.

Semaphore is written in Elixir. It uses a microservices architecture running on K8s or K3s and lightweight processes to achieve efficient, parallel builds and deployments.

The repository can be found here: https://github.com/semaphoreio/semaphore

The docs are quite detailed (I wrote them), and can be found here: https://docs.semaphoreci.com