If you need to upload an SVG file as the Theme Loader Spinner, you can follow the below instructions.

Install and activate the Child Theme that you will find in the downloaded theme package.

Then you will need to add 2 code snippets, one in the style.css and the other in the functions.php files of the child theme folder respectively.

Add the below CSS snippet in the style.css:

.grve-custom-spinner {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%,-50%);
}

and now add the below in the functions.php file:

function movedo_grve_print_theme_loader() {
    $page_transition = movedo_grve_option('page_transition');
    $show_spinner = movedo_grve_option('show_spinner');

    $movedo_grve_loader_classes = array();
    if( 'none' != $page_transition ) {
        $movedo_grve_loader_classes[] = 'grve-page-transition';
        $movedo_grve_loader_classes[] = 'grve-' . $page_transition . '-transition';
    }

    $movedo_grve_loader_classes = implode( ' ', $movedo_grve_loader_classes );

    if ( movedo_grve_check_theme_loader_visibility() ) {
?>
    <!-- LOADER -->
    <div id="grve-loader-overflow" class="<?php echo esc_attr( $movedo_grve_loader_classes ); ?>">
        <?php if( '0' != $show_spinner ) { ?>
        <div class="grve-custom-spinner">
            <svg width="90px" height="90px" viewBox="0 0 90 90">
                <path fill="#3B80FF" d="M90,90 L70.15125,70.15125 C68.6925,68.6925 67.5,65.80875 67.5,63.75 L67.5,45 L45,67.5 L22.5,45 L22.5,63.75 C22.5,65.80875 21.3075,68.6925 19.84875,70.15125 L0,90 L0,-1.95761774e-14 L45,45 L90,-1.95761774e-14 L90,90 Z" id="Logo"></path>
            </svg>
        </div>
        <?php } ?>
    </div>
<?php
    }
}

Replace the SVG code that you will find inside the functions.php file with your own and save.