Thanks for using the dev forum, it is good to see you again.
You can use 0 for the userID, which will present the chatController and allow the user to chat with the entire meeting at once.
Otherwise, you can specify another userID to present the chatController to send a message privately to one user.
The reason meetingService.presentMeetingChatViewController(self, userId: Int(meetingService.myselfUserID())) does not work is because you cannot send a chat to yourself.
Let me know if you have any other questions.
Thanks!
Michael