MacOS Catalina Sidecar and unsupported devices.
If anyone has an older Mac and would like to try the sidecar feature open up terminal and paste the following:
defaults write com.apple.sidecar.display AllowAllDevices -bool true; defaults write com.apple.sidecar.display hasShownPref -bool true; open /System/Library/PreferencePanes/Sidecar.prefPane
There isn’t any lag on my Early 15 Air and iPad 6th Gen but the quality is lacking somewhat, but this could be down to it being Beta 1. More devices may be supported in future releases though.