I have been searching for information about the teaching mode setup using the 2.xx firmware (the original instructions no longer apply), but couldn't find any references here. So I contacted Autel support and here is their reply:
Hope this helps and happy flying.
Thank you for contacting Autel Robotics support! The issue you are facing is related to the latest firmware version. In this version the teaching mode process is automated once you have both RC's connected via the training cable, but both RC's have to be updated to the latest version. If the second RC is not, you have to go through the process of binding it to your drone and updating it to the latest firmware. Once both RC's are up to date and you have the training cable plugged in, the roles should be automatically assigned to each RC. If you have any further questions or issue feel free to ask.
Hope this helps and happy flying.