So I've been discussing this over on Reddit, and a user there had success by skipping all quests (including Armour Fit For the Wild) and making straight for the Apothecary quest.
It does mean fighting Thalla with no upgrades at all, which is a bit of a pain on Path of the Damned, but once done, the quest triggered.
This cannot be the intended mechanism for triggering it, as surely Armour Fit for the Wild is the precursor to it.
Needs addressing.