Basically, this involves changing $wgWBClientSettings['sendEchoNotification'] to true.
We suggest this plan for deployment:
All the Wikivoyages
Announcement: May 3rd
Deployment: May 9th
All the Wikipedias but en, fr, de
Announcement: May 16th
Deployment: May 30th
(Wikispecies, Mediawiki, Wikiversity, Wikibook, Wikisource, Wikiquote, Commons...)
Announcement: May 30th
Deployment: June 13th
Wikipedias en, fr, de
Announcement: August 22th
Deployment: Sept 5th
Between each step, there is room for feedbacks and fixing issues if necessary.
(schedule from https://phabricator.wikimedia.org/T142103#3223284)