I’ve just installed Shotcut on Ubuntu 22.04 and crashed into this bug. Color picker do not work as expected (gives black frame) in the wayland session (being it the default one on Ubuntu and most linux distro now). I tested flatpak, snap and appimage versions.
I also tried to log out and log in with the Xorg legacy session. It does work there so it seems it is definitely related to Wayland. This is not a workaround for me as I much prefer Wayland session (as an example I cannot use touchpad gestures in xorg).
As it is now becoming default on most of distro (latest being KDE Plasma) I feel a fix is needed.
EDIT: A possibly related bug was reported here Color Picker Malfunction but I posted here as I think problem on linux is more strictly wayland related.