If you’re going to use https:// instead of http://, then you don’t need to have a clearText carve out in your network_security_config.xml. (In fact, you probably don’t need a network_security_config.xml file at all.)
If you are asking about the syntax inside of cleartextTrafficPermitted="true", I recommend formatting it just like the example.
I decided to try just switching all my http:// calls to https:// to see if I could save myself the hassle of setting up and keeping track of network_security_config.xml files, and everything worked fine, so I never actually ended up implementing cleartextTrafficPermitted.
Finally I found out how to access not secured local ressources (HTTP instead of HTTPS) on Android > 8
The difficulty for me was to find where I had to create the network_security_config.xml file, it must be in the …myProject\AndroidResources\res\xml folder
With that simple content :