I have been unable to change the screen resolution for a Linux Lite 6.x VM running in Hyper-V. I edited the /etc/default/grub file to change GRUB_CMDLINE_LINUX and GRUB_CMDLINE_LINUX_DEFAULT to add video=hyperv_fb:1920x1080 (followed by sudo update-grub, shutting down both the VM and Hyper-V before restarting), but it had no effect.
I also tried installing linux-image-extras with the hyperv-drivers (sudo apt-get install linux-image-extra-virtual), followed by a reboot, with no effect.
I realize this is a common issue; I've seen lots of people asking about it. The one thing that's different for me is that I also have an Ubuntu 22.04 LTS VM and a Zorin OS Lite VM (the latter of which is xfce-based, just like Linux Lite). I can resize the display on both of those instances; only Linux Lite is not resizable. As far as I know, I installed all the VM's following the same procedure with the same settings (e.g., Guest Services is activated in all three machines).