Ok, as far as I see it works now.

@Robert, the problem is still present for non-logged in users. There is currently no pagination enabled due to applying this workaround noted previously.

Robert, as a workaround, I've increased the topics shown in the topic area from 30 be 500.

That's just a cache. Please change it back to 20 or 15 for topics and posts. Delete all cache and leave some URL here.

Robert, I've changed from 500->20 topics, deleted the caches and now again non-logged in view sees only 20 topics without pagination. Eg:

https://egpu.io/forums/mac-setup/     (topic 1..20)
https://egpu.io/forums/mac-setup/paged/2/   (topic 21..40)
https://egpu.io/forums/mac-setup/paged/3/ (topic 41..60)

etc..

Any clues as to why the pagination refuses to appear?

I'm sorry but I have no clue what's wrong on your website.  Please wait for the next wpForo release, it may fix this issue.