CLEARTEXT communication to host not permitted by network security policy

I updated my android phone to the latest OS and now I can't consume the APIs on my DEV backend that does not use https.
I only have certificates for a few domains and for my test environment i don't have one, so i've been using http.

Now of course i get the

CLEARTEXT communication to <my-subdomain.com> not permitted by network security policy

exception.

I tried adding a security_config.xml file to the android project like explained here:
https://stackoverflow.com/questions/52968315/cleartext-http-traffic-to-server-com-not-permitted

but I get an exception as soon as the app starts:

Unhandled Exception:

Java.Lang.RuntimeException:

The I tried to add
android:usesCleartextTraffic="true"
to the application node in AndroidManifest, but I get another exception:

Unhandled Exception:

Java.Lang.RuntimeException: Unable to get provider com.google.firebase.provider.FirebaseInitProvider: android.content.res.Resources$NotFoundException: Unable to find resource ID #0x7f080003

Is there a solution?

Thanks!