Dave’s suggestion is the best if what you want is something like kbin, because it is, well, kbin but with work continuing on it.

A popular example mbin instance, if you want to take a glance to see what it looks like:

Example: http://fedia.io/

Mbin (and its parent, kbin) for those not familiar, aims to provide functionality with both Reddit-style/forum Lemmy instances and Twitter-style/microblogging Mastodon instances in one instance type and on one account, so if you’re gung-ho on Mastodon, that might be interesting to you.

If you’re just looking for a compatible-with-lemmy-but-not-lemmy server, and not specifically in search for something like kbin:

Piefed

Example: https://piefed.social/

Sublinks

Example: https://demo.sublinks.org/

The demo Sublinks server doesn’t seem to be yet federated with other server types; I don’t know what the status of development is.

If you’re okay with lemmy, but don’t like the lemmy Web UI, then there are some alternative frontends. These can run on a lemmy instance alongside the normal Web UI. My own home instance runs several, which you can take a look at. A number of other lemmy instances also do so:

mlmym (a lookalike for old.reddit.com):

Example: https://old.lemmy.today/

Photon (looks like it’s not working on my home instance ATM, so here’s lemmy.world’s):

Example: https://photon.lemmy.world/

Voyager:

Example: https://m.lemmy.today/posts/lemmy.today/all

Alexandrite:

Example: https://alexandrite.lemmy.today/lemmy.today

slemmy:

Example: https://slemmy.libdb.so/

leanish:

Example: https://natoboram.github.io/Leanish/

lemmyBB: I don’t know of functioning instances running this one, but they may be out there.

seconding this. despite the url, the instance i am on runs mbin and it’s the bees knees

man, thanks for this, i’ve been looking for an android app for mbin, for it feels like forever, and right there on that site, it’s just sitting there, Interstellar for Android, beauty, works great. party on excellent.