I can't register new users on iOS or Android app both Element or Element X. But I can register new users when using Mac OS desktop apps (Element and Element X).
When on iOS; Element can register users and Element X can't, says your homeserver needs to be upgraded to support matrix authentication service and account creation.
When on Android; Element can't register users, Says .well-known not available and Element X can't, your homeserver needs to be upgraded to support matrix authentication service and account creation.
I am hosting matrixdotorg/synapse docker on Ubuntu and cloudflare tunnel. It works but registration has to be done using the desktop apps then I can log in to Element X but not Element on android and can on both apps on iOS.