This has NOT been fixed on native iOS for the touch or controller HUD . I have not confirmed native android. It has been fixed on mobile for the touch and controller HUD when you use Xbox Cloud Gaming, Geforce Now, and Amazon Luna.
The map transparency setting also does not work on native iOS for the touch or controller HUD (android unconfirmed, works on Cloud Gaming).
Another Related Bug:
If you switch from controller input to touch input the map changes back to a square and is no longer transparent on mobile cloud gaming.