To solve the orientation of KDE at startup, I use another solution: I boot directly on the desktop, then a script immediately locks the screen, which is always oriented correctly, even on an external screen! And I can connect normally.
In case someone else comes across this in the future, my uConsole’s display was DSI-2. So sometimes it is different.
Run xrandr in the terminal. If xrandr shows XWAYLAND0 as the display device, it means that your DE is using Wayland. That display device is not the one you want. You’ll kind of have to “guess”. Try DSI-1. If that doesn’t work, try DSI-2.