diff --git a/plugins/ActivityPub/Util/Model/Activity.php b/plugins/ActivityPub/Util/Model/Activity.php
index ad99d34935..6df72542d2 100644
--- a/plugins/ActivityPub/Util/Model/Activity.php
+++ b/plugins/ActivityPub/Util/Model/Activity.php
@@ -63,8 +63,12 @@ class Activity extends Model
      * Create an Entity from an ActivityStreams 2.0 JSON string
      * This will persist new GSActivities, GSObjects, and APActivity
      *
+     * @param string|AbstractObject $json
+     * @param array $options
+     * @return ActivitypubActivity
      * @throws ClientExceptionInterface
      * @throws NoSuchActorException
+     * @throws NotImplementedException
      * @throws RedirectionExceptionInterface
      * @throws ServerExceptionInterface
      * @throws TransportExceptionInterface
@@ -74,9 +78,11 @@ class Activity extends Model
         $type_activity = \is_string($json) ? self::jsonToType($json) : $json;
 
         // Ditch known activities
-        $ap_act = ActivitypubActivity::getByPK(['activity_uri' => $type_activity->get('id')]);
-        if (!\is_null($ap_act)) {
-            return $ap_act;
+        if ($type_activity->has('id')) { // We can't dereference a transient activity
+            $ap_act = ActivitypubActivity::getByPK(['activity_uri' => $type_activity->get('id')]);
+            if (!\is_null($ap_act)) {
+                return $ap_act;
+            }
         }
 
         // Find Actor and Object
@@ -85,6 +91,7 @@ class Activity extends Model
         if (\is_string($type_object)) { // Retrieve it
             $type_object = ActivityPub::getObjectByUri($type_object, try_online: true);
         } else { // Encapsulated, if we have it locally, prefer it
+            // TODO: Test authority of activity over object
             $type_object = ActivityPub::getObjectByUri($type_object->get('id'), try_online: false) ?? $type_object;
         }
 
@@ -113,9 +120,9 @@ class Activity extends Model
             case 'Undo':
                 $object_type = $type_object instanceof AbstractObject ? match ($type_object->get('type')) {
                     'Note' => \App\Entity\Note::class,
-                    // no break
                     default => throw new NotImplementedException('Unsupported Undo of Object Activity.'),
                 } : $type_object::class;
+
                 switch ($object_type) {
                     case GSActivity::class:
                         switch ($type_object->getVerb()) {
@@ -126,6 +133,9 @@ class Activity extends Model
                         break;
                 }
                 break;
+            case 'Announce':
+                ActivityAnnounce::handle_core_activity($actor, $type_activity, $type_object, $ap_act);
+                break;
         }
         return $ap_act;
     }
diff --git a/plugins/ActivityPub/Util/Model/ActivityAnnounce.php b/plugins/ActivityPub/Util/Model/ActivityAnnounce.php
new file mode 100644
index 0000000000..a3cfc87a6a
--- /dev/null
+++ b/plugins/ActivityPub/Util/Model/ActivityAnnounce.php
@@ -0,0 +1,71 @@
+<?php
+
+declare(strict_types=1);
+
+// {{{ License
+// This file is part of GNU social - https://www.gnu.org/software/social
+//
+// GNU social is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// GNU social is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with GNU social.  If not, see <http://www.gnu.org/licenses/>.
+// }}}
+
+/**
+ * ActivityPub implementation for GNU social
+ *
+ * @package   GNUsocial
+ * @category  ActivityPub
+ *
+ * @author    Diogo Peralta Cordeiro <@diogo.site>
+ * @copyright 2021 Free Software Foundation, Inc http://www.fsf.org
+ * @license   https://www.gnu.org/licenses/agpl.html GNU AGPL v3 or later
+ */
+
+namespace Plugin\ActivityPub\Util\Model;
+
+use ActivityPhp\Type\AbstractObject;
+use Plugin\ActivityPub\Entity\ActivitypubActivity;
+
+/**
+ * This class handles translation between JSON and ActivityPub Announces
+ *
+ * @copyright 2021 Free Software Foundation, Inc http://www.fsf.org
+ * @license   https://www.gnu.org/licenses/agpl.html GNU AGPL v3 or later
+ */
+class ActivityAnnounce extends Activity
+{
+    protected static function handle_core_activity(\App\Entity\Actor $actor, AbstractObject $type_activity, mixed $type_object, ?ActivitypubActivity &$ap_act): ActivitypubActivity
+    {
+        // The only core Announce we recognise is for (transitive) activities coming from Group actors
+        if ($actor->isGroup()) {
+            if ($type_object instanceof AbstractObject) {
+                $actual_to = array_flip(is_string($type_object->get('to')) ? [$type_object->get('to')] : $type_object->get('to'));
+                $actual_cc = array_flip(is_string($type_object->get('cc')) ? [$type_object->get('cc')] : $type_object->get('cc'));
+                $actual_cc[$type_activity->get('actor')] = true; // Add group to targets
+                foreach (is_string($type_activity->get('to')) ? [$type_activity->get('to')] : $type_activity->get('to') as $to) {
+                    if ($to !== 'https://www.w3.org/ns/activitystreams#Public') {
+                        $actual_to[$to] = true;
+                    }
+                }
+                foreach (is_string($type_activity->get('cc')) ? [$type_activity->get('cc')] : $type_activity->get('cc') as $cc) {
+                    if ($cc !== 'https://www.w3.org/ns/activitystreams#Public') {
+                        $actual_cc[$cc] = true;
+                    }
+                }
+                $type_object->set('to', array_keys($actual_to));
+                $type_object->set('cc', array_keys($actual_cc));
+                $ap_act = self::fromJson($type_object);
+            }
+        }
+        return $ap_act ?? ($ap_act = $type_object);
+    }
+}
diff --git a/plugins/ActivityPub/Util/Model/Note.php b/plugins/ActivityPub/Util/Model/Note.php
index a294f6c01a..b0c4cd3e98 100644
--- a/plugins/ActivityPub/Util/Model/Note.php
+++ b/plugins/ActivityPub/Util/Model/Note.php
@@ -274,7 +274,7 @@ class Note extends Model
                         'canonical'     => $canonical_tag,
                         'note_id'       => $obj->getId(),
                         'use_canonical' => $ap_tag->get('canonical') ?? false,
-                        'language_id'   => $lang_id,
+                        'language_id'   => $lang_id ?? null,
                     ]));
                     Cache::pushList("tag-{$canonical_tag}", $obj);
                     foreach (Tag::cacheKeys($canonical_tag) as $key) {
diff --git a/plugins/RepeatNote/RepeatNote.php b/plugins/RepeatNote/RepeatNote.php
index 8e2661fc56..7e223f26c9 100644
--- a/plugins/RepeatNote/RepeatNote.php
+++ b/plugins/RepeatNote/RepeatNote.php
@@ -356,7 +356,7 @@ class RepeatNote extends NoteHandlerPlugin
      */
     private function activitypub_handler(Actor $actor, \ActivityPhp\Type\AbstractObject $type_activity, mixed $type_object, ?\Plugin\ActivityPub\Entity\ActivitypubActivity &$ap_act): bool
     {
-        if (!\in_array($type_activity->get('type'), ['Announce', 'Undo'])) {
+        if (!\in_array($type_activity->get('type'), ['Announce', 'Undo']) || !$actor->isPerson()) {
             return Event::next;
         }
         if ($type_activity->get('type') === 'Announce') { // Repeat