Cordova Android: Can I get any information on underlying Java/HTTP exceptions

Question

I have an Ionic/Cordova Android application that is deployed on various different client internal networks, where the application connects to a http service running on that internal network, using the Angular HTTP client.

Recently one of our clients finally upgraded from Android 5 to Android 12, and the application would no longer connect to the server, where they were using a self-signed HTTP certificate.

Following information here, we see the following:

The default configuration for apps targeting Android 6.0 (API level 23) and lower is as follows:

<base-config cleartextTrafficPermitted="true">
    <trust-anchors>
        <certificates src="system" />
        <certificates src="user" />
    </trust-anchors>
</base-config>

So I added this to the manifest file, ie in config.xml I added

<edit-config file="app/src/main/AndroidManifest.xml" mode="merge" target="/manifest/application" xmlns:android="http://schemas.android.com/apk/res/android">
        <application android:networkSecurityConfig="@xml/network_security_config" />
  </edit-config>

And this solved the problem on that particular network.

I also tested this on my office using both http and https and all worked fine.

Now I have another client where they are not using certificates, just unsecured http (I also have android:usesCleartextTraffic="true"), and their connection no longer works. The Angular http client just returns status code 0. Whenever there are any weird issues with network, this is all I ever get, with absolutely no information as to what is wrong.

My question is, underneath, would there be any extra native (Java) exception information logged to any sort of application/system, log, where I could see what is going wrong here, as I have no idea and connect reproduce the problem (I cannot get to the server in question, is is behind a firewall in another country), so any diagnostics need to be run on a client's mobile device, so I cannot install any SDK, root the phone etc, turn on dev mode etc. I just want to see if there are any errors logged (as you could, for example on a Windows desktop event viewer).

Is there any way to get any extra information on what may be going with the HTTP call here?