There's an open issue for that kind of thing here: https://github.com/LemmyNet/lemmy/issues/818

This isn't a bad idea, but I think my priority in that situation would be some kind of feature the suppresses duplicate posts. I sub to multiple world news communities for example because they do get different posts, but also people post the same thing in several communities at the same time so I see a lot of duplicate posts. And only seeing news f.ex would only make the dupes even more frequent because they're not interspersed with other communities.

Yeah, I'm missing this so hard from Reddit :( It should be possible to group subs I'm not subscribed to too!

If I understand it right, this is a feature developed from inception on Piefed. I'll just say it here: it's like multireddits. They have default comm group feed, at least on piefed.social. But you also can make your own group feed. Just like multireddit.

I personally would move to a piefed instance once it's more developed and have more choices for front end client / mobile app, since that's the biggest thing I miss from reddit.

Edit: and IIRC piefed also group same posts from different duplicate / similar comms into one "post".

I was literally in the middle of thinking about community groups when I came across your post, I think a lot of people would use this feature.