Lemmy

If you can identify exactly which things you like about old.reddit, you'll have a much better chance of getting them as settings on Lemmy.

There is LemmyBB as an alternative frontend based on phpBB: https://github.com/LemmyNet/lemmyBB

An example instance run by the Lemmy developers: https://fedibb.ml/

I'm pretty sure you can create your own bootstrap theme. If someone makes an old.reddit theme for Lemmy I'll add it to my instance.

PSA: you can choose your default theme in your profile settings. I'm pretty sure the themes available are determined by your home instance's options

Lemmy's UI in its current state is quite a bit of a mess. Hopefully this influx of users will result in devs that can help fix things.

There's an excellent style available through userstyles that might make the experience more bearable. If you have some technical skill and time, you could make one that looks and behaves as old.reddit. I expect something like that will appear soon there as I hear more and more complaints about the UI.

There is also https://brutalinks.tech/

(Source-code: https://sr.ht/~mariusor/brutalinks/ )

It's not a Lemmy frontend, but an unrelated project similar to Kbin that also uses ActivityPub to federate. I am however not sure how well it federates with Lemmy right now. Probably needs some testing and bug-fixing.

On paper there's lemmy-lite, but I don't know if any instance supports it.

I really like the look of LemmyBB. It's an alternative front-end for Lemmy that has the look of an "old internet" forum website. A few instances use it, but I haven't looked into it enough to know if it federates well.

The best thing about Lemmy is how it is completely separated from its UI. There are already different UIs available you can install to your instance or ask your admin to install. I think the LemmyBB might interest you: https://github.com/LemmyNet/lemmyBB

It will only be temporary. I don’t get why they don’t close for new accounts for a few days though.