mastodon.online is one of the many independent Mastodon servers you can use to participate in the fediverse.
A newer server operated by the Mastodon gGmbH non-profit

Server stats:

11K
active users

rendering is done client side. Interactive framerates for up to 40 million particles

written in javascript and uses three.js

if you can get your data into numpy you can get it into firefly

not just for N-body sims: can vis observations, like Sloan galaxies or GAIA DR3