Most communities seem to be moving over to Discord, which is by no means a valid Reddit replacement (in my opinion at least) but it is the only option with decent popularity and moderation tools that are not completely unusable at scale. Lemmy is being thrown around as a "proper" Reddit alternative, but realistically it will probably meet the same fate as Mastodon: plenty of people will try it for a week or so, only to realize that the platform sucks and the content simply isn't there.