I was also a little concerned when I saw this in the release notes earlier today. Why not make this opt-in (with a warning explaining the reasoning behind it) rather than opt-out via about:config?!

I think the most spiritually correct solution would be to use PeerTube considering that it’s also a federated system and therefore can interact nicely with Lemmy.

Absolutely! I use Elfeed in Emacs together with elfeed-org to help me to manage my feeds.

For example, we are on lemmy.world, but, for example, !plugins@sh.itjust.works is on another instance, which is lemmy.zip.

!plugins@sh.itjust.works is on the sh.itjust.works instance.

Is there any way for me to subscribe to it without making an account on that instance?

Yes indeed! Just search for the community in lemmy.world (as !plugins@sh.itjust.works), visit the community page on lemmy.world and hit “Subscribe”.

Will I be able to comment/post there without an account on that specific instance, but by using my lemmy.world account?

Yes, once you’ve subscribed just create posts and comment away as if it was a community on lemmy.world.

If you implement IP over smoke signals then perhaps :)

Every user, post, community, etc. on each of these services is represented as an ActivityPub object. Let’s take the example of following your Lemmy user from Mastodon. I can search for @Gohos@lemmy.ml in Mastodon and in the background my Mastodon instance will issue the following WebFinger request to lemmy.ml: https://lemmy.ml/.well-known/webfinger?resource=acct:Gohos@lemmy.ml. This will return the following JSON: -

{
  "subject": "acct:Gohos@lemmy.ml",
  "links": [
    {
      "rel": "http://webfinger.net/rel/profile-page",
      "type": "text/html",
      "href": "https://lemmy.ml/u/Gohos"
    },
    {
      "rel": "self",
      "type": "application/activity+json",
      "href": "https://lemmy.ml/u/Gohos",
      "properties": {
        "https://www.w3.org/ns/activitystreams#type": "Person"
      }
    }
  ]
}

From here I can request the application/activity+json URL at https://lemmy.ml/u/Gohos and if I request JSON I get: -

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    "https://w3id.org/security/v1",
    {
      "lemmy": "https://join-lemmy.org/ns#",
      "litepub": "http://litepub.social/ns#",
      "pt": "https://joinpeertube.org/ns#",
      "sc": "http://schema.org/",
      "ChatMessage": "litepub:ChatMessage",
      "commentsEnabled": "pt:commentsEnabled",
      "sensitive": "as:sensitive",
      "matrixUserId": "lemmy:matrixUserId",
      "postingRestrictedToMods": "lemmy:postingRestrictedToMods",
      "removeData": "lemmy:removeData",
      "stickied": "lemmy:stickied",
      "moderators": {
        "@type": "@id",
        "@id": "lemmy:moderators"
      },
      "expires": "as:endTime",
      "distinguished": "lemmy:distinguished",
      "language": "sc:inLanguage",
      "identifier": "sc:identifier"
    }
  ],
  "type": "Person",
  "id": "https://lemmy.ml/u/Gohos",
  "preferredUsername": "Gohos",
  "inbox": "https://lemmy.ml/u/Gohos/inbox",
  "outbox": "https://lemmy.ml/u/Gohos/outbox",
  "publicKey": {
    "id": "https://lemmy.ml/u/Gohos#main-key",
    "owner": "https://lemmy.ml/u/Gohos",
    "publicKeyPem": "-----BEGIN PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAwDc9TbmcvR/eRx0zuXl5\nqUu8vwcU3K1/70BqLdae/HtbjqXoHbVUI3exSVOTLVmPQ4oHjf6Lq5axyRRwihTh\nbDgWYSBCqZ07L6VrgXVg2APCkFpX32XlbFbbMQDXf+kodj6YrzwelXEJ03eTDKaa\nuFkFt0Uelu1k0AZVydGYT3U2iZ0jNGvpUMWQycTJ/k0r8n61JLuEMkvkVlH4ZDGb\nGTjwjLRds/zawe8FAK/Grn+AW/UTmW/1kBLcqhkeRYzWhyrVy+/f9jf03s0rW92w\n8PWM02AAE9edIpnK2XgElfkVWJenQzw7WDp045XPHMlUh5iizAJGcPAzdeEVNLq8\nGQIDAQAB\n-----END PUBLIC KEY-----\n"
  },
  "endpoints": {
    "sharedInbox": "https://lemmy.ml/inbox"
  },
  "published": "2023-06-03T17:30:16.990908+00:00"
}

This includes two important properties: inbox and outbox. Using ActivityPub I now know I can send you a message by POSTing a request to your inbox and I can fetch posts, comments, etc. you’ve made via your outbox.

Your public key is also included. This is how, if you sent me a message, I can verify that the message actually came from you.

That’s a very brief overview but I hope that helps!

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