Audinaut-subsonic-app-android/app/src/main/res/xml/network_security_config.xml

<?xml version="1.0" encoding="utf-8"?>

<network-security-config>
    <base-config cleartextTrafficPermitted="true">
        <trust-anchors>
            <!-- Trust preinstalled CAs -->
            <certificates src="system"/>

            <!-- Additionally trust user added CAs -->
            <certificates src="user"/>
        </trust-anchors>
    </base-config>
</network-security-config>