I tried to set this up for my site, because Disqus takes two hours to load and I don't like the centralization aspect and all the bloat they're adding. However, I stumbled first thing on the "host" parameter. It doesn't seem to like the subdomain I've set up for serving the comments, and it's obviously not getting served on the top-level domain, so I don't know what it expects. The documentation doesn't mention much…
A host can also be a subdomain. I'm using Isso on my personal blog for reference: https://blog.posativ.org/ . It works exact the same way as for a top-level domain.
Regardless, it works quite well now, thank you!