The criteria here is opaque, and doesn't necessarily make sense. If you're talking about "open source project to use due to ease of use", Ubuntu might be in th

The criteria here is opaque, and doesn't necessarily make sense. If you're talking about "open source project to use due to ease of use", Ubuntu might be in the top ten. Maybe. But if you're talking about an open source project to contribute to because the "community is huge, international, and diverse", and "the project offers a wealth of online documentation to help new contributors get started", that sounds like Debian, which is what Ubuntu (and countless other) distributions are based on. On top of that, if you don't like the default desktop, not only is it easy to change for you, but the Debian developers are much more likely to listen to your input on the defaults. What's more, if you find something wrong in Debian, in any part, you can get the source and fix it. Can't say the same about Ubuntu with it's binary-only drivers.