It is now possible for editors to opt-in (and out) of using Flow on their user talkpages via Special:Preferences#mw-prefsection-betafeatures on this wiki. This BetaFeature will NOT be automatically enabled, even if the user has "Automatically enable all new beta features" checked.
Editors who opt-in, will be shown a short (3-step) GuidedTour, and their old talkpage will be archived (the process takes a few seconds). Opting-out of this feature will move the Flow board to a subpage and un-archive the previous talkpage. More details and discussion are at phab:T98270 and linked tasks.
Please let us know if you experience any problems, either here, or at Talk:Flow, or on IRC in #wikimedia-collaboration. Thanks.