Sort of off-topic, but interesting engine, which I never heard about (wasn't ever mentioned on HN either: https://hn.algolia.com/?q=Iceshrimp):
>Iceshrimp is a decentralized and federated social networking service, implementing the ActivityPub standard.
The Iceshrimp devs are also working on a "port" to .NET that's basically a brand new social media app, but with an upgrade path from the JavaScript version.
I also use Iceshrimp to self-host my own fediverse account and I think it's pretty good software. I think it has a better UI that Mastodon and it has some cutesy features that Mastodon lacks, like being able to emoji-react to posts.