As a webdev I only consider alternatives that implement ActivityPub which is what drawn me to Lemmy. Other parties have come out with Reddit-like but a lot are still closed gardens under unknown people's control. I trust the W3C on this one.
Tildes is the only other alternative that I know besides lemmy. It's more focused on discussion, as you probably know. Personally, though, I doubt it can scratch my reddit itch. I do enjoy discussions, but I also need my "nonsense stuff" fix like memes. I do like what they're trying to do. I think they're a good complementary site to lemmy if someone is ditching reddit altogether.
If the site is not federated, it's not possible to leave it without also leaving all its content behind.
There’s also kbin, which seems to be compatible with lemmy.
I would argue that for most purposes, kbin IS lemmy. It has 1/10th the native user-count and 1/100th the native comment count according to https://the-federation.info/platform/73 and https://the-federation.info/platform/184. I get the sense that a large part of what people use kbin for is as an alternative UI to access lemmy communities. It seems much further from achieving a critical mass of native communities though.
That's not a knock on kbin, people use it an enjoy it. But I'd contend that to the extent that either kbin or lemmy are "reddit replacements" at all, they act together as a single federated option with multiple UX's rather than two discrete options.
I kind of don't necessarily want another locked in non-federated site to replace reddit when we have lemmy and other potentially better / less locked in options.
That said, I'm not against standalone forums, so tildes.net ... well, it looks like a currently less successful lemmy instance with about the same or less engagement, and I can't see how one would sign up if one wanted to. Last I heard there was an invite process? No thanks really.
You also need to really define "reddit alternative" - do you mean a forum? Or something trying like lemmy to be a sort of clone? In the "forum" link aggregation option, there's HackerNews. There's the BBS The Well. There's sort of internet service provider focused forums like dslreports.com.
Yo dawg can I get a tildes invite?
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