People consider vegans on Lemmy as too preachy. Even in vegan communities here, mods have to remove soooo many inappropriate comments (I read a few of these and they keep getting removed for good reasons). Comments that suggest going vegan on posts about animal abuse are downvoted.
At the same time, whenever there is something about Windows or Chromium based browsers, people here are doing exactly the same. “Just use Linux/Firefox/whatever”.
You are in the fedi, a fringe social space generally uses by IT focused people. People love their linux here because these instances are probably all hosted on Linux. People are here because they left traditional social media.
I’m not saying veganism isn’t welcome here. You just have a ton of tech people here. If reddit tried to ban vegans instead of punch advertising down people’s throats you would have more vegans instead of people who use Firefox.