Found on superuser.com: https://superuser.com/a/1680613
sudo apt install linux-image-extra-virtual
Open grub configuraiton first:
sudo vi /etc/default/grub
Change line with GRUB_CMDLINE_LINUX_DEFAULT to
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash video=hyperv_fb:1920x1080"
Update grub:
sudo update-grub
Shutdown the linux virtual machine.
set-vmvideo -vmname ubuntu -horizontalresolution 1920 -verticalresolution 1080 -resolutiontype single