https://utteranc.es/
I used a Python export and conversion script that I found at https://pawamoy.github.io/posts/migrate-disqus-comments-to-u... , and made a couple updates to it (and then commented on that post with my changes).
Pretty happy with it so far.
Here's a couple of my posts that show Utterances in action, one that has a lot of the migrated comments, and one with mostly new comments:
- https://blog.isquaredsoftware.com/2020/05/blogged-answers-a-...
- https://blog.isquaredsoftware.com/2021/01/context-redux-diff...