Come help out with Apache Airflow! It's a great project to get involved with because it has a ton of users and real world problems, but it's still early enough that there's low hanging fruit in terms of adding functionality and improving existing code.
A helpful place to start is the provider packages, since Airflow has integrations with so many 3rd party providers, and if you have knowledge in any of them it can be a good jumping off point.
https://github.com/apache/airflow/