- Open Terminal
sudo vi /etc/default/grub
- Add following line in end
GRUB_CMDLINE_LINUX="… quiet splash video=hyperv_fb:1920x1080"
- Update file
- Run on terminal
sudo grub2-mkconfig -o /boot/grub2/grub.cfg
- Reboot Virtual Machine
- Write this command on terminal
sudo grubby --update-kernel=ALL --args="video=hyperv_fb:1280x1024"
- Reboot
Method 1 works in Fedora 34 just after reboot you have to go into the setting and manually change the resolution it gives the option of the resolutions after doing the steps or at least it worked that way for me