Hi everyone,
I recently installed Ubuntu 26.04 on my older HP ProBook (around 2015), and I'm having a problem with my external ASUS monitor.
My setup
- Laptop: HP ProBook, around 2015
- OS: Ubuntu 26.04, freshly installed yesterday
- External monitor: ASUS
- Connection: VGA cable
- Previous OS: Windows
What happened
The ASUS monitor worked perfectly when I was using Windows.
Before installing Ubuntu, I also booted Ubuntu 26.04 from a USB stick in Live mode, and the external monitor worked normally there too.
However, after installing Ubuntu 26.04 onto the laptop, the external monitor stopped working.
The ASUS monitor simply displays:
The important thing is that Ubuntu doesn't detect the second monitor at all. If I go to:
Settings → Displays
I only see the laptop's built-in display. There is no second/ASUS monitor available to configure.
I also tried logging out because I was advised to check whether I could switch between Wayland and Xorg/X11 from the login screen. However, I don't see the settings/gear icon underneath the password field, so I don't have an obvious way to select another session.
I'm not sure whether I'm actually using Wayland or Xorg.
Things I know so far
- ASUS monitor + VGA cable work with Windows.
- ASUS monitor worked when Ubuntu 26.04 was running from the Live USB.
- ASUS monitor does not work after installing Ubuntu 26.04.
- Ubuntu's Settings → Displays does not detect the external monitor.
- I don't see a Wayland/Xorg selection icon on the login screen.
I'm guessing this could be related to the graphics driver, kernel, VGA output configuration, or the difference between the Live USB environment and the installed system.
I'm not very experienced with Linux graphics, so I'd really appreciate step by step troubleshooting.
I can provide the output of commands such as:
echo $XDG_SESSION_TYPE
lspci | grep -E "VGA|3D|Display"
uname -r
and anything else that would help diagnose the problem.
Why would VGA work perfectly in the Ubuntu 26.04 Live USB but completely stop working after installing Ubuntu to the internal drive?
And is there a way to determine whether I'm using Wayland or Xorg and whether the VGA output is being detected at the hardware/driver level?
Thanks in advance!