@jernej__s You mean opt-out? I haven't installed this version yet, but the above thread says that the default setting is to allow the telemetry, meaning it's on the user to opt out of it, right?

(If I read “opt-in” as a noun instead of an adjective, I can interpret the sentence as “Firefox opted the users into the tracking”, but that's still contrary to the usual meaning of the term. To opt in to something, you have to actively request it.)