I had some troubles with running Classic with ConsolePort on the ROG Ally and made a topic about it here ConsolePort on ROG Ally - Support / Technical Support - World of Warcraft Forums (blizzard.com)
Just wanted to inform what caused the problem for me and to let people know who experience the same issue the way to solve it who come search here on the Technical Forums. You just simply change DirectX 12 to DirectX 11 in the settings.
Happy gaming!