It’s doesn’t seem like feddit.online is aware of the other community (forumlibre@jlai.lu), so it doesn’t have a copy of both posts, so it doesn’t know that they are cross-posts.

If you bring that community into feddit.online, then create a post with the same URL as a recent post (e.g. https://files.catbox.moe/pebvir.jpeg), then they’ll show up.

The picture (or whatever external resource a post is pointing to, like https://bbc.com/news/article.html)

The post you mentioned (‘melting is tough’) isn’t picked up as a cross-post on PieFed instances because the dates are too far apart. A restriction that Rimu wanted was that they should only be detected if they were within 7 days of one another.

However, if you take that URL (https://lemmy.world/pictrs/image/91f96cc8-a194-4cb8-abc6-505261e65420.jpeg), and make a new post with it, then the post you mentioned now shows that it has a cross-post.

A cross-post is just a post that links to the same URL as another post. The codeberg Issue that Blaze linked to mentions an exception, but other than that, there’s not a convenient button that copy-pastes a post’s title, body, and URL into a new ‘Create Post’ form. You can do it manually though, and everything that receives it will detect it as a cross-post, because everything is just looking for matching URLs.

Photon came up in this discussion amongst the Lemmy developers.

Maybe it was Neon Modem Overdrive, or this TUI app.

But, yeah - shell browsers like the ones you mentioned don’t support JavaScript, so won’t work with Lemmy (as it currently is - it might be different when they start using the leptos-based UI). There’s places where they’re not great with PieFed either (e.g. link2 -g can’t deal with WEBP images), but it’s completely theme-able, so a theme could easily be added by someone suitably invested to overwrite the existing HTML and provide a better experience.

If an admin bans a local user, they’re banned once, but if they ban a remote user, the way Lemmy currently handles it is to ban them from every community they’ve subscribed to. There’s an Issue about it because it’s a hacky and incomplete solution. As such, the ‘banned 20 times’ thing isn’t something that people should read too much into.