Please note that Screens 4 is no longer available and has been replaced by Screens 5, a universal app for iPhone, iPad, Mac, and Vision Pro.
Screens doesn't support authentication against system user accounts on non-Macs. That is to say, you can't use, for example, your Linux system log-in credentials in Screens as you can with a Mac (using the Mac User authentication method). The authentication credentials configured in the remote VNC server settings must be used.
If you experience an unsupported authentication method error when attempting to connect to a non-Mac, the destination computer's VNC server is likely configured with the Unix Password authentication option. Set it to VNC Password instead.