@jolamar Thank you for PR! It was added in 0.15.3

This is AWESOME - only one question - given that content-state is a nested item ( like alert), how do you leverage $push->setContentState to assign the desired (and number of) key/values?

Hmm... Please check the example in the bottom of this comment - #161 (comment)
Is that what you want to achieve?

$payload = Payload::create()
            ->setTimestamp(Carbon::now()->timestamp)
            ->setEvent('update')
            ->setRelevanceScore(75.0)
            ->setStaleDate(Carbon::now()->addMinutes(60)->timestamp)
            ->setContentState(['ourScore' => 54, 'opponentScore' => 23]);

Content state can be anything you defined in your LiveActivityAttributes (Swift). So passing in an array should be enough.
Here is how they define the key in the docs https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_notification_server/generating_a_remote_notification#2943363

The updated or final content for a Live Activity. The content of this dictionary must match the data you describe with your custom ActivityAttributes implementation. For more information, see Updating and ending your Live Activity with remote push notifications.

in Token.php we also need to add the pushtype for live activities ApnsTopic. I'll get another PR out for this but in case you need it now.

public function generateApnsTopic(string $pushType)
    {
        switch ($pushType) {
            case 'voip':
                return $this->appBundleId . '.voip';

            case 'liveactivity':
                return $this->appBundleId . '.push-type.liveactivity';

            case 'complication':
                return $this->appBundleId . '.complication';

            case 'fileprovider':
                return $this->appBundleId . '.pushkit.fileprovider';

            default:
                return $this->appBundleId;
        }
    }

Details here https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_notification_server/sending_notification_requests_to_apns