I have seen that the platform have a few seo navigation and crawl issues. Here are the problems
Point 1. You’ve implemented rel=‘next’/‘prev’ but not as a meta tag but as a item prop. You’ve put in canonical only in Topics but not properly in Categories.
https://meta.discourse.org/c/feature & https://meta.discourse.org/c/feature/l/latest?page=1 both have the same canonical <link rel="canonical" href="https://meta.discourse.org/c/feature" /> whereas it should be different for both the pages.
Point 2. NOSCRIPT URL : Plugin for signatures? & Plugin for signatures?
PushState URL: Plugin for signatures? & Plugin for signatures? - #2 by cpradio
Point 3. Refer point 1 answer