Android - MediaStore download does not work on API level 28 or lower

Question

I'm writing a piece of Android code which stores a file in the user's download folder.

@CapacitorPlugin(name = "Downloads")
class DownloadsPlugin : Plugin() {
    @PluginMethod(returnType = PluginMethod.RETURN_NONE)
    fun download(call: PluginCall) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
            val filename = call.getString("fileName")!!
            val data = call.getString("data")!!

            val contentValues = ContentValues().apply {
                put(MediaStore.MediaColumns.DISPLAY_NAME, filename)
                put(MediaStore.MediaColumns.RELATIVE_PATH, Environment.DIRECTORY_DOWNLOADS)
            }

            val contentResolver = context.contentResolver
            val uri =
                contentResolver.insert(MediaStore.Files.getContentUri("external"), contentValues)!!
            val outputStream = contentResolver.openOutputStream(uri)!!

            outputStream.write(data.toByteArray(StandardCharsets.UTF_8))
        }

        call.resolve()
    }
}

The code I've written works correctly on Android 10 (API level 29) or higher. On API level 28 or lower, the code does not work. On calling the download method, the following error is logged:

2022-10-08 16:10:59.064 23121-23184/com.example.example E/Capacitor: Serious error executing plugin
    java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Method.invoke(Native Method)
        at com.getcapacitor.PluginHandle.invoke(PluginHandle.java:125)
        at com.getcapacitor.Bridge.lambda$callPluginMethod$0$com-getcapacitor-Bridge(Bridge.java:706)
        at com.getcapacitor.Bridge$$ExternalSyntheticLambda5.run(Unknown Source:8)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:193)
        at android.os.HandlerThread.run(HandlerThread.java:65)
     Caused by: java.lang.IllegalArgumentException: no path was provided when inserting new file
        at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:165)
        at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:135)
        at android.content.ContentProviderProxy.insert(ContentProviderNative.java:476)
        at android.content.ContentResolver.insert(ContentResolver.java:1587)
        at com.example.example.DownloadsPlugin.download(DownloadsPlugin.kt:36)
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.getcapacitor.PluginHandle.invoke(PluginHandle.java:125) 
        at com.getcapacitor.Bridge.lambda$callPluginMethod$0$com-getcapacitor-Bridge(Bridge.java:706) 
        at com.getcapacitor.Bridge$$ExternalSyntheticLambda5.run(Unknown Source:8) 
        at android.os.Handler.handleCallback(Handler.java:873) 
        at android.os.Handler.dispatchMessage(Handler.java:99) 
        at android.os.Looper.loop(Looper.java:193) 
        at android.os.HandlerThread.run(HandlerThread.java:65) 

How can I correct this error so that the code works on API level 28 or lower?