I've got quite a few actually that I know about. ( commento ++ is used for AnonUpload's blog ) - I want to make my own solution that works with the existing acc system, just not sure how I would pull it off. Dockerized solutions would be awesome, but PHP implementations would work just as well! Paid or free.
Chirp, Commento, Commento ++, Isso, and Coral are ones I currently know of.