Debian
One of the oldest and most influential Linux distributions, run by volunteers under a formal democratic constitution.
Debian is a free operating system built by volunteers since 1993. You may never have installed it directly, but you have almost certainly used it: Ubuntu, Raspberry Pi OS and a great many web servers are built on top of it. Its reputation rests on being conservative and thorough rather than fast, which is exactly what you want underneath something that has to keep running.
What makes Debian unusual is its governance. The project has a written constitution, elects a project leader, and settles contested questions through a formal ballot called a General Resolution, in which accredited Debian Developers rank the options. That is why its August 2026 vote on whether large language models may be used to write Debian code drew so much attention: few technical communities decide such things by an actual vote.