The one being promoted the most on migrations subreddits is Kbin (particularly kbin.social for sign-up). It federates with Lemmy as well - apparently some folks think the Lemmy devs have questionable moral character so decided not to promote Lemmy as a primary option (hell if I know, didn't look into it).
That Kbin instance is getting slammed and trying to scale up right now - many identical /r/{subreddit} are now available at /m/{subreddit} (m for magazine) thanks to some of the prior subreddit mods I guess?
That Kbin instance is getting slammed and trying to scale up right now - many identical /r/{subreddit} are now available at /m/{subreddit} (m for magazine) thanks to some of the prior subreddit mods I guess?