KDE

While you can follow across the Fediverse, no matter the platform, not all kinds of cross platform follows make sense imo. I personally wouldn't follow Lemmy stuff from my Mastodon because it can get really floody. I also wouldn't generally follow Mastodon accounts from Pixelfed, or Lemmy from Pixelfed. It's really great that you can, but sometimes it's better to just make an account on the specific platform instead.

You don't login, you just access it from Mastodon.

Hello from Lemmy.zip

@talesofaprinny @kde I'm not sure how helpful this will be for you, but it's kind of like email. You have an account on one email server (like, say, Gmail), and you can use that account to exchange messages in a standard format with people on other email servers (Outlook, Yahoo Mail, Proton Mail, Fastmail, etc.), but your account on Gmail doesn't let you log in anywhere else. If you want to use any of those other servers directly, you need to create an account on the server you want to use.

Similarly, you can use your account on one Fediverse server (mastodon.social) to exchange messages in a standard format with people on other Fediverse servers (techhub.social, lemmy.kde.social, etc.), but your account on mastodon.social doesn't let you log in anywhere else. If you want to use any of this other servers directly, you need to create an account on the server you want to use.

You don't. You follow @[email protected] and at them when you want to post a thread there. Everyone commenting there should appear as an answer on Mastodon.