There are active Discords for "Vulkan", "DirectX" and "Graphics Programming".

https://gamedev.net/forums/ is the classic hang-out spot.

For rust, the bevy community is pretty great

mastodon.gamedev.place is a thing

I'm sad that Lemmy didn't catch on, I had high hopes for a distributed Reddit replacement

But I think it's a combination of "people have short memories" and "people don't like change"

I think discoverability and fragmentation are bigger problems that the fediverse needs to solve for adoption to take off.