No notifcations for forum / fetch user for fetching content

src/Model/Post/UserNotification.php

@@ -33,6 +33,7 @@ use Friendica\Model\Contact;
 use Friendica\Model\Post;
 use Friendica\Model\Subscription;
 use Friendica\Model\Tag;
+use Friendica\Model\User;
 use Friendica\Navigation\Notifications;
 use Friendica\Network\HTTPException;
 use Friendica\Protocol\Activity;
@@ -176,6 +177,11 @@ class UserNotification
 			return;
 		}
 
+		$user = User::getById($uid, ['account-type']);
+		if (in_array($user['account-type'], [User::ACCOUNT_TYPE_COMMUNITY, User::ACCOUNT_TYPE_RELAY])) {
+			return;
+		}
+
 		$notification_type = self::TYPE_NONE;
 
 		if (self::checkShared($item, $uid)) {

src/Protocol/ActivityPub/Receiver.php

@@ -263,7 +263,19 @@ class Receiver
 	{
 		$id = JsonLD::fetchElement($activity, '@id');
 		if (!empty($id) && !$trust_source) {
-			$fetched_activity = ActivityPub::fetchContent($id, $uid ?? 0);
+			if (empty($uid)) {
+				$actor = JsonLD::fetchElement($activity, 'as:actor', '@id');
+				if (empty($actor)) {
+					$actor = '';
+				}
+	
+				// Fetch a user out of the receivers of the message.
+				$fetch_uid = Receiver::getBestUserForActivity($activity, $actor);
+			} else {
+				$fetch_uid = $uid;
+			}
+
+			$fetched_activity = ActivityPub::fetchContent($id, $fetch_uid);
 			if (!empty($fetched_activity)) {
 				$object = JsonLD::compact($fetched_activity);
 				$fetched_id = JsonLD::fetchElement($object, '@id');
@@ -643,6 +655,29 @@ class Receiver
 		}
 	}
 
+	/**
+	 * Fetch a user id from an activity array
+	 *
+	 * @param array  $activity
+	 * @param string $actor
+	 *
+	 * @return int   user id
+	 */
+	private static function getBestUserForActivity(array $activity, string $actor)
+	{
+		$uid = 0;
+		$receivers = self::getReceivers($activity, $actor);
+		foreach ($receivers as $receiver) {
+			if ($receiver['type'] == self::TARGET_GLOBAL) {
+				return 0;
+			}
+			if (empty($uid) || ($receiver['type'] == self::TARGET_TO)) {
+				$uid = $receiver['uid'];
+			}
+		}
+		return $uid;
+	}
+
 	/**
 	 * Fetch the receiver list from an activity array
 	 *