The actual HDMI Dummy Plug Headless Ghost Display Emulators haven't arrived yet." : r/techsupportgore
DTech HDMI Dummy Plug 4K Headless Ghost Display Emulator Compatible with Windows Mac OSX Linux Support 4kx2k 1080x2160 for Computer Desktop (fit-Headless, 2 Pack): Amazon.co.uk: Computers & Accessories
4K HDMI Dummy Plug,Virtual Monitor Display Emulator, Headless Display Adapter Supports up to 3840x2160@60Hz, 1080@120Hz DVI EDID Emulator - Walmart.com