Make sure to read https://developer.rocket.chat/rocket.chat/iframe-integration/adding-a-rocket.chat-chat-room-to-your-web-app
There are two important settings there:
Administration > Settings > General > Restrict access to any iframe
needs to be disabledAdministration > Settings > General > iframe Integration > Enable Receive
needs to be enabled- Keep
Receive Origins
as*
- Open Xcode and create a new iOS project.