Jellyfin, we are moving away from Reddit and we are pleased to announce our new forum!

https://beehaw.org/post/642061

Jellyfin, we are moving away from Reddit and we are pleased to announce our new forum! - Beehaw

official twitter announcement https://twitter.com/jellyfin/status/1670589982665322496 [https://twitter.com/jellyfin/status/1670589982665322496]

I'm sure Jellyfin considered the Fediverse but some projects like the idea of having more control of the community discussions they participate in so having a forum makes sense. I still think a Jellyfin community on Lemmy can thrive with an official forum in place.
Jellyfin is all about self hosting. I don't see why they wouldn't just create their own Lemmy instance if that was the concern. It wouldn't need to be big if they limited the userbase

Lemmy is pretty immature, and probably doesn't suit their needs compared to a forum.

They don't really need a link aggregator, so using Lemmy there wouldn't really make much sense.

The only thing that they might use Lemmy for is the community, but otherwise, it's not a great fit for what they need.

Yup, "when you have a hammer, everything looks like a nail". Lemmy and the Fediverse are great, but they aren't the end all, be all solution to online content.
Lemmy and KBin are cool and all, but VERY rough around the edges so I wouldn't expect large projects or communities not directly related to then to adopt either. Keep in mind for most of these projects, they picked Reddit because the users were already there and the software was relatively polished. These are both things that many of us users are interested in improving, but that projects with communities aren't going to want to use until theyre already more advances than they are right now