Same issue here. Window is transparent with Nvidia 550.67-2, Cura and 5* version, ArchLinux, Wayland, Plasma or Gnome. Start either using X11 works fine. Cura 4.13.1 works fine under Wayland. However, running Cura 5.6.0 in Wayland on Debian 12 stable, Gnome 44.8-1, it works fine. A clue?