krusader not following gtk theme

Krusader's window manager follows Openbox config, but not GTK theme.
setting QT_QPA_PLATFORMTHEME=gtk2 does not fix
setting QT_QPA_PLATFORMTHEME=gtk3 changes to a default gtk3 light theme, but won't follow further theme config
maybe needs qt5-styleplugins or equivalent installed in container?

all other apps in container follow set themes, just not Krusader itself