I had great success with using DIY PiKVMv2 on a Pi Zero W + CSI board to access my home PC when I went away in October last year - many, many thanks to everyone who helped create it.
So I didn’t bother to test it properly when going away again recently, and of course it didn’t work: the V of KVM wouldn’t show any video. (I could do some of what I needed via the terminal, but it was still annoying.)
I knew it wasn’t that I had forgotten to switch the PCs HDMI output to the Pi. (If I try sending it to both the monitor and the Pi, nothing is happy, thanks to the refresh rate issue.)
Trying it on my return shows that the issue was having the video mode set to ‘Direct H.264’ (blank screen on the remote device) rather than having it as ‘WebRTC H.264’ (works).
I don’t remember changing any settings from the ones that worked in October, and I was using the same browser tab both times. Did this setting get reset in the various PiKVM software updates since then, or has something affecting this changed in them? Should ‘direct’ work on a Pi Zero 2 W?
Either way, lesson learnt: test it properly before leaving! 