I spend 1 hour figuring out why my Raspberry Pi 4 model B with Sense HAT wouldn't even boot without HDMI monitor connected. I ended up with these in
/boot/config.txt which worked:
hdmi_force_hotplug=1 hdmi_group=2 hdmi_mode=82
Is there a more beginner-friendly way to setup Raspberry Pi for remote connectivity with VNC Viewer?