Always show the upload container by default

functions.php

<?php

// check if function does not exists
if ( ! function_exists( 'rtmedia_after_media_gallery_show_upload_button' ) ) {
	function rtmedia_after_media_gallery_show_upload_button() {

		// Please change the page_slug from here
		$page_slug = 'file-upload';

		if ( isset( $_GET[ $page_slug ] ) && ! empty( $_GET[ $page_slug ] ) ) {
			?>
			<style type="text/css">
				#rtm-media-gallery-uploader {
					display: block !important;
				}

				#rtm-media-options .rtmedia-upload-media-link {
					display: none;
				}
			</style>
			<?php
		}
	}
}
add_action( 'rtmedia_after_media_gallery', 'rtmedia_after_media_gallery_show_upload_button', 10 );