Normally, I would vote for opt-in only, but I think that it could be opt-out for Firefox as long as there are no dark patterns that make it difficult to opt-out

Normally, I would vote for opt-in only, but I think that it could be opt-out for Firefox as long as there are no dark patterns that make it difficult to opt-out. The survival of Firefox is extremely important for the future of the Web. If it is opt-out, then Mozilla would have to be extremely open about how to opt-out and exactly what is tracked.