Magento 2.3 : File Upload issue in UI Component Form

Please replace your UI Component with following code.

Change imageUploader instead of fileUploader in your formElement.

       <field name="ffl">
            <argument name="data" xsi:type="array">
                <item name="config" xsi:type="array">
                    <item name="dataType" xsi:type="string">string</item>
                    <item name="source" xsi:type="string">ffl</item>
                    <item name="label" xsi:type="string" translate="true">Licence Pdf</item>
                    <item name="visible" xsi:type="boolean">true</item>
                    <!-- - Remove fileUploader -->
                    <!-- + Add imageUploader -->
                    <item name="formElement" xsi:type="string">imageUploader</item>
                    <item name="required" xsi:type="boolean">true</item>
                    <item name="uploaderConfig" xsi:type="array">
                        <item name="url" xsi:type="url" path="ffl/ffl/fflupload"/>
                    </item>
                </item>
            </argument>
        </field>