Shameless plug: My friend and I are building a federated commenting system on top of Matrix if anyone is interested. You control the data, your users choose where they want to be signed up, and the system will not disappear overnight because a company decides to discontinue it. And of course there are no trackers/pixels.
This is a hobby project that we're launching in three weeks. If you are interested, come talk to us on matrix (https://matrix.to/#/#cactus:bordum.dk) or keep an eye on our (for now dummy-) landing page: https://cactus.chat/, https://gitlab.com/cactus-comments