I would say that most vegans, even if they've never heard it, at least approximately follow the Vegan Society's famous definition:
Veganism is a philosophy and way of living which seeks to exclude—as far as is possible and practicable—all forms of exploitation of, and cruelty to, animals for food, clothing or any other purpose; and by extension, promotes the development and use of animal-free alternatives for the benefit of animals, humans and the environment. In dietary terms it denotes the practice of dispensing with all products derived wholly or partly from animals.
Striking the parts that seem irrelevant to this specific question:
Veganism is a philosophy and way of living which seeks to exclude—as far as is possible and practicable—all forms of exploitation of, and cruelty to, animals for [...] any [...] purpose [...]
Keep in mind that "animals" in that first part is widely treated as "humans and non-human animals". So you would have to decide 1) to what extent cruelty was inflicted to create the distro, 2) to what extent people and non-human animals were exploited to create the distro, and 3) if there exist practicable alternatives that meaningfully reduce (1) and (2).
Two of those (x-fit and linux) are mostly good for the user whereas veganism is good for everyone but capitalists so, I would hope, they'd talk about being Vegan first
As a linux user who uses linux on my linux machine (which runs linux), I agree that mentioning that one uses linux is not as important as mentioning that non-linux thing you just said