You can contribute by doing code reviews on PRs. Even if your contribution is only to ask “What does this do?” it can help locate places where code isn’t easily readable.
Obviously use your judgment, but code review commenting is a nice way to get up to speed on a project, improve your own coding skills, and is valuable to the project too.
I had an apprenticeship once at a dev shop where everybody was leagues above me. As basically the lowest-level coder both in status and in skill, I was surprised to find out my “curriculum” included doing code reviews on very senior people’s code.
Now I swear by the practice. It’s kinda like anyone can be a therapist if they know how to listen. Anyone can provide value with code review if they keep their eyes open and communicate honestly.