In my experience this mostly doesn't exist. For a public open source-only project, sure, you can use a variety of free simple CI/CD solutions. But as soon as you need anything more complicated than "run a public linter on my public code", you need to add plumbing that makes it complicated.
I am very interested in making the simplest possible CI method and deployment method, but I've never been able to make or use anything that wasn't complicated. The least-complicated solution I have ever seen is Drone.io, but even that's not all that simple.
In my experience this mostly doesn't exist. For a public open source-only project, sure, you can use a variety of free simple CI/CD solutions. But as soon as you need anything more complicated than "run a public linter on my public code", you need to add plumbing that makes it complicated.
I am very interested in making the simplest possible CI method and deployment method, but I've never been able to make or use anything that wasn't complicated. The least-complicated solution I have ever seen is Drone.io, but even that's not all that simple.