If you set the language(s), it will show only posts with tha language (is set) on your feed, otherwise shows all languages.
https://join-lemmy.org/docs/users/06-other-features.html#language-tags
Most posts don’t have a language defined (undefined), don’t know if they’ll also show on your feed.
Kinda, you should use @[email protected] but won’t show anything, you need to follow, after that when new posts are made all posts and comments will show as reply on mastodon.
There’s an issue about it https://github.com/LemmyNet/lemmy-ui/issues/1227
If you link !community@instance.tld the URL should be c/[email protected], instead ate the moment the URL is https://instance.tld/c/community
Go to communities and search for !vpn@lemmy.word or just vpn if already linked will show up.
Alternative you can open the URL directly, example you are on lemmy.ml then the URL is lemmy.ml/c/[email protected]
It could be defined by the instance or community
https://join-lemmy.org/docs/users/06-other-features.html#language-tags