Most people use Linux, most people develop for Linux. The more Open Source OS'es are split up, the weaker they get. So it is best to use/support the big one and keep it strong. If BSD were the biggest, I'ld use that. For most people the technical differences don't matter.
Fosstodon is an English speaking Mastodon instance that is open to anyone who is interested in technology; particularly free & open source software.