The fediverse is working. I am now following (using Mastodon) a “Learning Rust” community on Lemmy [1], who I found through them commenting on my peertube video [2] using Lemmy.
[1] @learningrustandlemmy [2] https://diode.zone/w/wJJJ7DRh3fCvHq6KuZY3t9
Be aware that you won’t see a lot of the comments on any particular post in a Lemmy community when following via Mastodon. There’s a bit of a stalemate between the Lemmy Developers and the Mastodon Developers where they are each asking the other to bridge the gap of the incomplete federation.
Using another Mastodon-like service probably comes with additional similar issues.