I've made an active effort to bookmark any active forums I come across. Even Lemmy doesn't quite fill the niche that actual forums provide, though it is still useful.
Civfanatics. I actually joined up long before I ever signed up for Reddit. It's probably the one site besides Youtube that I've consistently used since middle school.
Lemmy still has a lot of problems reddit does, just smaller and weirder. It's probably not possible to create a "perfect" social media platform, but there still seems like room for a new type of social network that's federated but isn't a clone of something else.
I still use reddit for looking up information even after deleting my account. Yesterday i decided i wanted to compile the zen kernel for fedora. And reddit had the best guide for doing so. And what settings were worth a damn.