Mac OS 10.13, just like iOS, to use the App Transport Security key in the Info.plist to allow HTTP requests in an appliation
When I got the installer to run, the dropdowns would come up empty and the error log would state:
Installer version 3.2.0 (mac)
Unable to load http://flex.apache.org/installer/sdk-installer-config-4.0.xml
Error while trying to load XML configuration file: 2032
When ran from terminal I got:
Apache Flex SDK Installer[3746:297717] App Transport Security has blocked a cleartext HTTP (http://) resource load since it is insecure. Temporary exceptions can be configured via your app's Info.plist file.
I had to add to the /Applications/Apache Flex/Apache Flex SDK Installer.app/Contents/Info.plist:
Then I was able to select which SDKs to install.