The Drupal Content Management System (CMS) can be used with an open-source relational database management system (DBMS) like MySQL as well as a proprietary DBMS like Microsoft SQL Server to build web applications. This type of database uses a query language called structured query language (SQL) to store, access, and modify data in the database. During Drupal installation, it creates a database structure in the selected database that is used to store the Drupal site’s dynamic content and configurations.
Some open source organizations you can contribute to:
Open Archive
Eclipse Adoptium
Public Lab
Tensorflow
Open Wisp
Quarkus
Fedora
CNCF
CircuitVerse
Backdrop
Jenkins
JBOSS
ScoreLab
MetaCall
And the list goes on...these organizations usually take part in GSoc, GSoD etc.