Today we had the same problem. We could not deploy a excisting Android test app on a new Android 10 phone. The test app points to the local host IP adress ( e.g. http://192:168.1.10:8080 ) where the Mendix modeller is running. The test app works on other Android phones, but not on this phone. It took us a couple of hours to figure out why. (We are using Mendix 7, and test app excist already for almost 2 years)
This stackoverflow topic gave us the right direction to solve it. https://stackoverflow.com/questions/54752716/why-am-i-seeing-neterr-cleartext-not-permitted-errors-after-upgrading-to-cordo. For the local test server, you are using HTTP (for Mendix cloud HTTPS). As of Android 9, clear text communication (= HTTP) from a APP is disabled by default. To Allow HTTP, the useClearTextTrafic should be set activly to true.
The following should be added to your config.xml file within the Android Platform scope,
<splash src="res/android/screen-xxxhdpi-portrait.png" density="port-xxxhdpi"/>
<edit-config file="app/src/main/AndroidManifest.xml" mode="merge" target="/manifest/application">
<application android:usesCleartextTraffic="true" />
And the following should be added to the top op your config.xml file (see also the stackoverflow toppic)
Hope this help you and others solving the issue of not getting a test app running with the error cannot initialized app on Android 9/ Android 10 phones.