You can check out the Apache open source projects , they list the documentation requirement as a JIRA bug.

Apache NLP which needs documentation https://issues.apache.org/jira/issues/?jql=project+%3D+OPENN...

UN Online Volunteering This is on the social contribution side ,may not be your choice , but its good to know. https://www.onlinevolunteering.org/en/vol/opportunity_search...