Add Bricks CSS to Gravity Form Buttons.php

function add_brx_btn_css_to_gf( $button, $form ) {
    
    $fragment = WP_HTML_Processor::create_fragment( $button );
    $fragment->next_token();
    $fragment->add_class( 'brxe-button' );
    $fragment->add_class( 'bricks-button' );
    $fragment->add_class( 'bricks-background-primary' );

    return $fragment->get_updated_html();
    
}
add_filter( 'gform_submit_button', 'add_brx_btn_css_to_gf', 10, 2 );