Screenshots
Before and after builds (both with #10895's launcher fix), opening T3's own folder picker. The main window is identical everywhere; the only difference is the X11 class of the GTK picker when no portal is running (t3code to T3code). Also inlined in the description.
GNOME Shell 50.1, X11 without a portal:
GNOME X11 folder picker before and after
XFCE 4.20, X11 without a portal:
XFCE X11 folder picker before and after
GNOME Shell 50.1, native Wayland: