This kernel can enable HDMI only at fullscreen just like the 4.19 kernel and it is the same setup as before. Just edit your kernel command line and add something like this "video=eDP-1:d video=HDMI-1-A:e" That is for the Surface any model or check /sys/class/drm for your devices videocards. Here is a screenshot with the kernel and its 4K on my Surface Pro 3. Now you can use the ALSA plugin usb_stream in the big screen fullscreen. The kernel also has IPTS module as well the price is $2.00 USD.
https://paypal.me/RemixOS?country.x=CA&locale.x=en_US
https://paypal.me/RemixOS?country.x=CA&locale.x=en_US