DNT was a failure that shouldn't be depended on for anything.

Safari has already removed it in version 12.1 (https://developer.apple.com/documentation/safari_release_not...), so if that's the only opt-out mechanism there's no way for Safari users to make that choice. That probably includes all iOS users, since all iOS browsers just wrap Safari.

I wouldn't be surprised to see other browsers remove it eventually as well. Like Apple says, it ended up doing the exact opposite of what it was supposed to -- almost nobody obeys it anyway, and it hurts the privacy of people that try to use it by contributing an uncommon factor to their browser fingerprint.

This doesn't help the concern from enterprise users that they don't want their self-hosted software to phone home, ever.

Hello! Self-hosted users on EE are currently not affected, we opened an issue here to clarify: https://gitlab.com/gitlab-org/growth/product/issues/164

"Not yet" is small comfort.

DNT suffers from a lack of trust. I have turned it on by default, but I kind of assume that it's completely ignored.