I could find in GitHub the java source code of one of the Android setting app.

There I could find in (https://gerrit.dirtyunicorns.com/plugins/gitiles/android_packages_apps_Settings/+/2b2abac7148163dc6199b9dd304a6cebccbf310f/AndroidManifest.xml) its manifest the fragments as:

com.android.settings/.Settings$ManageExternalSourcesActivity
com.android.settings/.Settings$ManageAppExternalSourcesActivity

I have created an hidden entry in lockdown with them and now it opens the Unknown source configuration screen to end user choose to enable/disable to a specific app_name.

It shows a list with all apps that claims to install something.

I just could not identify yet how to open it already selected on the app_name to avoid end user to set something wrong.