their server is down right now, but it did federate with lemmy.ml before going down https://lemmy.ml/c/activitypub@community.nodebb.org
https://programming.dev/c/nodebb-development@community.nodebb.org
also you can read their announcement from their Mastodon profile @nodebb@fosstodon.org
edit: it's back up, to see the announcement post in Lemmy format, put this in your Lemmy's search: https://community.nodebb.org/post/102756
it's from !nodebb-development@community.nodebb.org
the bridge is pretty nice, I would recommend everyone on compatible platforms to use it (Bluesky, and probably any AP microblogging platform, but I've only tried it with Mastodon)