When trying to connect remote clients to Cygwin/X, I get 'Authorization required, but no authorization protocol specified'
Solution 1:
If you use VcXsrv, you should turn on "Disable access control" setting. But note, after that anyone from Network who has access to your X-server may show their UI on you X-server.
Solution 2:
You need to install the xhost Cygwin package, and after starting the X server, run the following (also on Cygwin):
$ DISPLAY=:0.0 xhost <remote_hostname_or_ip>
This command authorizes <remote_hostname_or_ip> (e.g. a WSL Ubuntu installation, a separate Linux system in the network, etc.) to connect to and use Cygwin/X.