I have an Intel Compute Stick with integrated Intel HD Graphics 515 video running Ubuntu 18.04 server (kernel 4.15.0-29-generic) without X windows. For remote access to this system I use TeamViewer, which apparently requires a framebuffer device (/dev/fbX) to run correctly. When I am booting the system with a monitor attached, framebuffer device is present and all is good. When I boot it without a monitor attached, there's no framebuffer device and TeamViewer cannot be used.
Before I upgraded to Ubutun 18.04, I was using Ubuntu 16.04 (4.4.0-116-generic) and it worked perfectly, with or without monitor.
One more piece of information which might help - after booting without a monitor, connecting a monitor when the system is already up is not detected and the monitor is useless (nothing is displayed). I must reboot in order to use the display
I am looking for a way to force the creation of the framebuffer device upon boot