@Catrope is currently working on this.

Change 564182 had a related patch set uploaded (by Catrope; owner: Catrope):
[mediawiki/extensions/GrowthExperiments@master] Suggested Edits: Add hidden preference for topics feature flag

https://gerrit.wikimedia.org/r/564182

Change 564183 had a related patch set uploaded (by Catrope; owner: Catrope):
[operations/mediawiki-config@master] GrowthExperiments: Enable topic search, behind a hidden preference

https://gerrit.wikimedia.org/r/564183

Once this is deployed, the following console snippet will enable topic matching in production:

new mw.Api().saveOption('growthexperiments-homepage-suggestededits-topics-enabled', 1).done( function() { window.location.reload() });

To turn it back off, change the 1 to 0.

Remember that whether topic matching is on or off also affects the activation workflow for suggested edits (in particular, the intro dialog), so you may also want to deactivate suggested edits and go through the activation workflow again:

new mw.Api().saveOption('growthexperiments-homepage-suggestededits-activated', 0).done( function() { window.location.reload() });

I've scheduled the config patch for the 19:00 UTC SWAT on Thursday Jan 16. The train should already have run by then (it's scheduled for 14:00-15:00 UTC).

Change 564182 merged by jenkins-bot:
[mediawiki/extensions/GrowthExperiments@master] Suggested Edits: Add hidden preference for topics feature flag

https://gerrit.wikimedia.org/r/564182

Change 564183 merged by jenkins-bot:
[operations/mediawiki-config@master] GrowthExperiments: Enable topic search, behind a hidden preference

https://gerrit.wikimedia.org/r/564183

Mentioned in SAL (#wikimedia-operations) [2020-01-16T19:33:18Z] <catrope@deploy1001> Synchronized wmf-config/InitialiseSettings.php: GrowthExperiments: Enable topic search, behind a hidden preference (T242698) (duration: 00m 56s)

Checked in all target wikis - seems to be working as expected.