When Twitter went downhill, we got bluesky and mastodon. Bluesky works as a decent Twitter replacement and Mastodon is smaller and more fediverse-focused. Lemmy and Piefed are alternatives to Reddit but I wouldnt really say that Lemmy fully replaces Reddits functionality in terms of niche subs. That’s why I’ve always been in favor of explosive growth here with each Reddit exodus, to have a forum within an order of magnitude or two of the size of Reddit to properly become a replacement.