We have lots of projects which are open to contributions and many which have very mature mechanisms for incorporating changes from a number of sources, however I can't think of any 'go-to' projects to recommend for the often asked question of "I'm new to programming/open source, where do I begin?".
In contrast, there seem to be an increasing number of communities and resources around getting people inducted and migrated to Linux, a multitude that are trying to "teach people to code" and plenty that will instill the virtues of FOSS, but not as many which are actively encouraging and coaching people to contribute to established projects.
If you are new to programming, you probably shouldn't dive into adding code to an established project that has a high quality bar. You should study the code, add documentation, and add tests.