Debian 11 here with LXDE (Xorg + lightdm)

How could I change the driver used by X?

My X is using the default options, I have no /etc/X11/xorg.conf file, so I generate one with the command sudo X -configure :1 and after that copying the contents of /root/xorg.conf.new to /etc/X11/xorg.conf

After reboot I have a running X on :0 like before (ps auxww | grep Xorg returns ... /usr/lib/xorg/Xorg -s 0 :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch), but with a blank screen (no EE in /var/log/Xorg.0.log file). If I remove that /etc/X11/xorg.conf file and reboot I have a normal screen again.

The generated /root/xorg.conf.new is this (removed commented options, some FontPaths and SubSections Display's, for brevity)

Section "ServerLayout"
    Identifier     "X.org Configured"
    Screen      0  "Screen0" 0 0
    InputDevice    "Mouse0" "CorePointer"
    InputDevice    "Keyboard0" "CoreKeyboard"
EndSection

Section "Files"
    ModulePath   "/usr/lib/xorg/modules"
    FontPath     "/usr/share/fonts/X11/misc"

    FontPath     "built-ins"
EndSection

Section "Module"
    Load  "glx"
EndSection

Section "InputDevice"
    Identifier  "Keyboard0"
    Driver      "kbd"
EndSection

Section "InputDevice"
    Identifier  "Mouse0"
    Driver      "mouse"
    Option      "Protocol" "auto"
    Option      "Device" "/dev/input/mice"
    Option      "ZAxisMapping" "4 5 6 7"
EndSection

Section "Monitor"
    Identifier   "Monitor0"
    VendorName   "Monitor Vendor"
    ModelName    "Monitor Model"
EndSection

Section "Device"
    Identifier  "Card0"
    Driver      "radeon"
    BusID       "PCI:0:2:0"
EndSection

Section "Screen"
    Identifier "Screen0"
    Device     "Card0"
    Monitor    "Monitor0"
    SubSection "Display"
        Viewport   0 0
        Depth     24
    EndSubSection
EndSection

Noticed that without an /etc/X11/xorg.conf file the output names returned by xrandr have a dash, like DP-1, DP-2 etc and with that file xrandr return those names without a dash: DP1, DP2...

The only change I want to do is replace:

Driver "radeon"

with

Driver "fbdev"

Already tried to remove the xserver-xorg-video-radeon package but it would break my system removing the WM, DE and a lot of other apps.