I was also an old.reddit user and that's probably why I like kbin more. It's not exactly the same but it does feel the closest. There's also browser add-ons to adjust the CSS of the site that makes it a bit closer.

Lemmy currently has more apps for mobile but there's an Apollo clone that's in beta for Kbin on iOS and android. Personally, I feel like Kbin has the better UI and the mobile site isn't a bad option until Artemis(the app in beta) comes out in a week or two.

I'm on kbin.social, but the other big one I see is lemmy.world. Kbin and lemmy have different UIs so it's whatever you prefer. There's also a lot of different instances of both you can join but you see posts from all the instances the one you join is federated with. It takes a sec to get used to.

There's a few that are going to try and stick around but, yeah, it's fucked. I've been on kbin for the last week and it's been a lot better so far. It's still going through growing pains but it's gotten a lot better even in the last week.