updates:
i installed and activated a discourse plugin that restores the preferred old behavior & functionality.
if it wasn’t already done for them, users can now individually un-mute the Trade category (preferences > categories). Trade activity is now cleared from the /latest view, but the category itself is once again navigable. it can be accessed by clicking the hamburger nav dropdown, just like all the other listed categories.
previously, the default “mute” setting forced by discourse upstream deleted the category from everyone’s view, including from the list of available categories. the new plugin fixes this: Trade posts are once again hidden from the front page by default, but the category itself is always listed and accessible via the dropdown, unless users have added it to their personal list of muted categories. the forum is now working as intended/expected.
thanks for your patience, folks!