I'm not familiar with the RetroLink cable but the Mayflash one you have to set to Wii U mode in order for Dolphin to properly use it. Also you have to change the driver that is assigned to it. This page should help - https://dolphin-emu.org/docs/guides/configuring-controllers/
Handz Gaming on YouTube: https://www.youtube.com/HandZ_gaming
The Retro Byte (Including Dolphin videos): https://tinyurl.com/TheRetroByte[url=https://www.youtube.com/playlist?list=PLh9SHYt4z-C-43uNJA8kuoYc1txrJPkxh][/url]
The Retro Byte (Including Dolphin videos): https://tinyurl.com/TheRetroByte[url=https://www.youtube.com/playlist?list=PLh9SHYt4z-C-43uNJA8kuoYc1txrJPkxh][/url]