Alternatively, Appveyor & Travis have fully free tiers. They don't even have my credit card number. CI is trivially forked, doesn't require configuring secrets per repository, etc. Being CI focused, both have configuration and UI oriented towards having a matrix of builds that can individually pass/fail for more granular results, and comes with various SVG badges for build status.
A concrete example of travis on a Rust project:
https://github.com/MaulingMonkey/bugsalot/blob/master/.travi...
https://travis-ci.org/github/MaulingMonkey/bugsalot/builds/6...
Linux/Windows/OSX unit testing, Android/iOS/WASM builds.
If you're using Gitlab and languages other than Java, there is nothing useful in this blog post.
There is a lot of bang for the buck here.
Edit. Serious question: why would you want to set up and maintain several different tools when you can have everything running in one place?
Heroku is $0/mo to start. heroku.com/free