@chougulemrudula double check what i have posted here in the hdmi section:
Specifically:
sudo apt update
sudo apt install read-edid xserver-xorg-video-fbdev x11-xserver-utils
and this xorg.conf:
#/etc/X11/xorg.conf
Section "Monitor"
Identifier "Builtin Default Monitor"
EndSection
Section "Device"
Identifier "Builtin Default fbdev Device 0"
Driver "fbdev"
EndSection
Section "Screen"
Identifier "Builtin Default fbdev Screen 0"
Device "Builtin Default fbdev Device 0"
Monitor "Builtin Default Monitor"
EndSection
Section "ServerLayout"
Identifier "Builtin Default Layout"
Screen "Builtin Default fbdev Screen 0"
EndSection
Regards,