How to emulate a vertical screen in Xubuntu guest?

I am using an Xubuntu guest virtual machine with Virt-Manager, Spice, and QXL. I want to rotate the virtual display to be vertical so as to fit my monitor.

Stuff I tried:

• Settings > Display in Xubuntu guest: There is a Rotation popup menu, but the only available option is None.
• Rotating via xrandr doesnt work:

~$ xrandr -q
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 8192 x 8192
Virtual-0 connected primary 1024x768+0+0 0mm x 0mm
   1024x768      59.95*+
   1920x1200     59.95  
   1920x1080     60.00  
   1600x1200     59.95  
   1680x1050     60.00  
   1400x1050     60.00  
   1280x1024     59.95  
   1440x900      59.99  
   1280x960      59.99  
   1280x854      59.95  
   1280x800      59.96  
   1280x720      59.97  
   1152x768      59.95  
   800x600       59.96  
   848x480       59.94  
   720x480       59.94  
   640x480       59.94  
Virtual-1 disconnected
Virtual-2 disconnected
Virtual-3 disconnected
~$ xrandr --output Virtual-0 --rotate right
xrandr: output Virtual-0 cannot use rotation "right" reflection "none"

• echo 3 | sudo tee /sys/class/graphics/fbcon/rotate had no effect and gave no error.
• As far as I can tell, I have the right drivers installed:

~$ apt list --installed | grep -i spice

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

spice-vdagent/bionic,now 0.17.0-1ubuntu2 amd64 [installed]
~$ apt list --installed | grep -i qxl

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

xserver-xorg-video-qxl/bionic,now 0.1.5-2build1 amd64 [installed]

• My XML looks OK, right?

    <graphics type='spice' autoport='yes'>
      <listen type='address'/>
      <image compression='off'/>
    </graphics>
    <sound model='ich9'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1b' function='0x0'/>
    </sound>
    <video>
      <model type='qxl' ram='65536' vram='65536' vgamem='16384' heads='1' primary='yes'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
    </video>

Is there a way to have a virtual vertical monitor with a Xubuntu guest?