Currently (version 24.02.2), the KDE Itirnerary Android app always uses Breeze light as a theme. There is no option to switch to the dark variant. Preferrably this should be changedrespecresp to respect Android’s dark mode setting.
Many apps also have a setting to force light / dark mode (KDE’s dektop apps use a menu entry for this). There should probably be a drop-down menu on the settings screen.