Splish, splash.
Found this: DietPi + Allo Web GUI: Now available, which lead me to this: https://www.computeraudiophile.com/forums/topic/43628-allo-gui-image-broken/?tab=comments#comment-832007
Just jump straight to the last one to see the workaround (quicker than doing a new image). Credit to @wakajazz for addressing originally.