I recently [[ https://monarchists.wiki/w/index.php?title=Special:Log&offset=20181107000000&limit=1&type=managewiki | enabled the TitleKey extension for Monarchists.Wiki ]], and I'm assuming that there's additional set-up or tasks necessary since searches don't work as well as I had hoped.
Auto-complete doesn't work for mainspace article unless the whole title is typed in the search. Other recently created wikis with the TitleKey extension (e.g. rottenwebsites.miraheze.org) have the same problem. Older wikis with TitleKey (e.g. AllTheTropes.org) don't have the problem.