Easy to miss, but the “prefix” in zogstrip’s post is not in monospace. i.e. it is not part of the setting name.
What was said is "category page style" is now “desktop category page style” in prep for the coming “mobile category page style” setting.
Anyway, I have two localhost versions of Discourse, latest and 1.6.0beta9
The 1.6.0beta9 version does not have a “category page style” setting.
It does have category style, but that is bar, box, bullet.
It does have the newer “hybrid” categories page. but I could not find any setting.
Things have changed since that version so there very well could have been a setting that was there between then and now. (Or maybe “top menu” took “classic” ?)
In any case, rather than hunt down a setting that may or may not be there, why not upgrade to latest?