It would be nice if manjaro.org or forum site admin add redirect from old forum pages. In first days i landed at least 10 times to a non existing link (if i remember correctly, it was from a global search engine?).
Today again, for example:
here is linked to dead(not redirected):
while the page was moved apparently to:
So maybe making old dead link pages noindex parameter and trying to reindex archived pages maybe using sitemap or such, google webmaster console?
Best would be to create .htaccess redirect from old pages to archive or importing archived to main forum so it is found