Q:

Sidecar only shows a black screen on iPad until reboot

It is 100% fixable by rebooting my Mac. It is also 100% annoying when I have to do that.
After the reboot I can use Sidecar wirelessly very reliably. Until I disconnect. Or change any Sidecar setting (Like: Show touch bar on/off). After that there is a good chance I have to reboot my Mac for it to work again.

Why does it do that?
How do I temporarily fix that? (Say: Is there a terminal command?)
How do I permanently fix that?

A:

I found that if you go to display preferences -> arrangement -> tick and then untick mirror display option it will work but I would have to repeat this step every time I use sidecar :)

