I am using Microsoft Remote Desktop to remote my Ubuntu Desktop 23.10 in my office without a monitor connecting.
you have to stop encrypt the password to prevent the system changing the remote password every reboot.
after that, add a fake dummy desktop so that we can remote into a GUI.
cd /usr/share/X11/xorg.conf.d
vi dummy.conf
Section "Monitor"
Identifier "Monitor0"
HorizSync 28.0-80.0
VertRefresh 48.0-75.0
# https://arachnoid.com/modelines/
# 1920x1080 @ 60.00 Hz (GTF) hsync: 67.08 kHz; pclk: 172.80 MHz
Modeline "1920x1080_60.00" 172.80 1920 2040 2248 2576 1080 1081 1084 1118 -HSync +Vsync
EndSection
Section "Device"
Identifier "renderD128"
Driver "dummy"
VideoRam 256000
EndSection
Section "Screen"
DefaultDepth 24
Identifier "Screen0"
Device "renderD128"
Monitor "Monitor0"
SubSection "Display"
Depth 24
Modes "1920x1080_60.00"
EndSubSection
EndSection
~ not you can remote at anytime.