more diagnostic information on <no signal> screen

[Krotu]

Is your feature request related to a problem? Please describe.
no signal or black screen for video are not very informative, extra information is available but requires terminal access and running commands that may not be known to users.

Describe the solution you'd like
diagnostic information presented on no signal screen or available in another window in the case of black screen

Additional context
v4l2-ctl --query-dv-timings gives some hints to where the issue is
link has been severed -> no hdmi connection
numerical result out of range -> resolution or refresh rate too high
and for non-cm4 it still detects 1080p 60hz -> 1080p 60hz not supported on this device