So everything broke.
Because while I've been putting off finishing the last couple of updates needed, Xenforo decided to release a major update that would break the custom theme we used. So I've tried to reimport the style as best as possible given the new template code in this version.
I managed to get most of the functionality back over an evening - however the Featured Map slider which has broken may not be fixable (the add-on dev last updated it in 2018 and left the internet), so that...