What is Git Actions in a brief? It's GitHub attempt to include Continues Integration on the platform so you can have all in one place: repo, CI and CD.

I will not go into comparison of what's better, feature and performance, but I rather give some tips of the problems, I've faced with Git Actions.

Check YAML yourself

There is no syntax checking inside you .yml files: some section missing, no error displayed. That's something they need to improve.

Add as many debug lines as you can.

We should not do checkin and let the CI test, right? we should test on our own. Yes, I know, but sometimes 2 minutes of debugging or looking into a stack trace helps you find the problem.

Maven: use maven.test.skip if building multiple time

Make sure you run the tests. But, if you're doing some chained actions like maven release or deploy, avoid running test multiple times in the same pipeline.

To have manual build, merge with "main"

You can trigger Git Actions using events like push, pull request and automatically the actions will be triggered. You can also trigger them manually with the workflow_dispatch option.
The point is that the yml must be merged in your main development branch (it used to be master, but is discouraged now).