AFAIK, Mlmym is the only "old" reddit UI. I'm not sure if it's still maintained or not but the last commit was sometime last year.
Didn't know Alexandrite wasn't maintained anymore. I liked it.
Tesseract is sort-of like "new" reddit circa 2023 but without all the crap. It's Lemmy only.
Voyager is also pretty popular, but not my cup of tea.
Blorp is I think relatively new but looks really nice. Haven't played with it much.
I'm a bit lost beyond those, but you can check out https://lemmyapps.com/ for a mostly up to date directory.