AFAIK, Windows Remote Desktop always renders through virtual display adapter devices, though it can optionally make use of GPU resources to accelerate rendering to these devices.
I just tested in an ESXi VM[1], and Windows 10 will happily boot and accept an RDP connection without any (virtual) display hardware at all:
https://jasomill.at/HeadlessRDP.png
Whether a particular computer will boot Windows without display hardware depends on the firmware — in my experience, some workstations will, some won't, and I honestly haven't seen a modern x86 server without some sort of integrated graphics to support out-of-band management, often with a VGA port as the only physical video output.
[1] By hand-editing the VM's .vmx configuration file, setting
svga.present = "FALSE"
and adding the undocumented option
hwm.svga.notAlwaysPresent = "TRUE"
Interesting aside: I figured this out by running "strings" on the hypervisor executable, which turned up this suspiciously Scheme-like bit of configuration code:
https://jasomill.at/vmx.ss.html#L-808
In fact, two definitions and a couple trivial syntax fixes are enough to get Chez Scheme to evaluate it without warnings:
$ awk -f - vmx.ss <<EOF | scheme -q
BEGIN {
print "(define / fxdiv)"
print "(define (log . args) (for-each display args))"
}
{
gsub(/\(\)/, "'()")
gsub(/ 0x/, " #x")
print
}
EOF
$
So it appears the VMware hypervisor contains an interpreter for a very Scheme-like dialect of Lisp.