The meta typesupport rosidl_typesupport_cpp is being used correctly and contains both typesupports: rosidl_typesupport_connext_cpp as well as rosidl_typesupport_introspection_cpp. I don’t see why both rmw implementations can’t extract their matching typesupport.
Reviewing the conversation you mentioned that you have sourced the setup file after building the workspace but your steps above don’t include that (Talker example issue with Beta 1). Can you please post the LD_LIBRARY_PATH from the shell you run the talker from.
I am sorry. I don’t know what else to debug.