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    [KDE] Black screen on VNC after setting display scale

    I installed kubuntu 20.04 on a server. There is a low-res monitor (1600x1200) connected to the console. I want to connect to the server using VNC (tigervncserver) from a system with a high-res/high-DPI monitor (3840x2160).

    After starting tigervnc and connecting to the server, a window is displayed with (as expected) very small text. I set the Global Scale to 200% and select "Save display properties: For only this specific display arrangement". The display listed is VNC-0.
    When I kill and restart vncserver and connect with vncviewer, I see the plasma startup screen and then the screen goes black. If I wait long enough, the lock screen is displayed. When unlocked, the screen returns to black.

    If I delete ~/.local/share/kscreen and reboot, I am again able to connect to the server with vnc, with the scaling set to 200% for all displays. (On occasion I have had to reboot in recovery mode for this to work.) If I try to log in on the system console in graphics mode while connected with VNC, I get a screen frozen with the startup splash screen. I get a pop-up on the vnc window saying "kwin_x11 closed unexpectedly" and it goes black. I can kill vncserver and restart and get a responsive screen when I reconnect. If I have logged in on the console before connecting with vnc, the error messages sometimes shows up there before both console being unresponsive and vnc window going black.

    I can work around this mess by starting the system console in text mode, but display-specific scaling is broken.

    #2
    This might be relevant:
    https://github.com/TigerVNC/tigervnc/issues/1240
    You might need to run the vnc server with x0vncserver instead of vncserver, depending on if you are logging in to a running x11 session, or a new one.
    You may also need to use a different login manager instead of SDDM.

    Other than investigating different VNC server implementations, it also may be worth looking at Plasma's KRDC and KRFB native server/client options.

    it has been ages since I used any sort of remote desktop, except krdc/krfb recently , just to see if it worked and take some screenshots for a post reply.
    I recall that each different server had it own quirks and use cases, so I stopped using them altogether.

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