How can I detect programmatically if the Android Device is in Dark Mode?

Use the following code:

boolean isDarkThemeOn = (getResources().getConfiguration().uiMode & Configuration.UI_MODE_NIGHT_MASK)  == Configuration.UI_MODE_NIGHT_YES;

You first need to do this changes in manifest

<activity
    android:name=".MyActivity"
    android:configChanges="uiMode" />

then onConfigurationChanged of activity

val currentNightMode = resources.configuration.uiMode and Configuration.UI_MODE_NIGHT_MASK
when (currentNightMode) {
    Configuration.UI_MODE_NIGHT_NO -> {} // Night mode is not active, we're using the light theme
    Configuration.UI_MODE_NIGHT_YES -> {} // Night mode is active, we're using dark theme
}

Okay finally found the solution I was looking for. As @deepak-s-gavkar points out the parameter that gives us that information is on the Configuration. So, after a small search I found this article that gives this example method that has worked perfectly for what I wanted:

fun isDarkTheme(activity: Activity): Boolean {
        return activity.resources.configuration.uiMode and
                Configuration.UI_MODE_NIGHT_MASK == Configuration.UI_MODE_NIGHT_YES
    }