I just learned that while DisplayPort is hot plug compatible on Linux NVIDIA proprietary drivers, HDMI 2.0 (SPECIFICALLY 2.0 resolutions) are not hot plug compatible. It’s extremely inconsistent because if the Xserver isn’t seeing the monitor it booted from, it just throws a tantrum and refuses to display anything, not unless you plug things in “nth” times, it’s almost random. ONLY HDMI 2.0 resolutions suffer this issue.
Also, if you’re using EDID emulators compatible with HDMI 2.0 and you’re in EDID copy mode, do not turn on Freesync at all with the monitor you’re copying the EDID from. If you flip the Freesync switch on your monitor behind a EDID emulator, the GPU feeds a different EDID than the one the monitor expects and doesn’t output anything and just sees garbage. Same might happen for Atomos devices. (or it could be lumped into the NVIDIA Linux HDMI 2.0 hotplug bug)
Recopying with the Freesync bit on works, but will throw compatibility out the window if you’ve got a splitter downstream.
Seems no one has brought this up because people haven’t been swapping monitors over HDMI 2.0. They just boot with a fixed set. But HDMI 2.0 is definitely not hot plug friendly on NVIDIA Linux drivers. The problem doubles up if the EDID changes in the same boot.