How to add aria-label to logo?

You can use a filter like this:https://docs.generatepress.com/article/generate_logo_output/

In your case, try this, replace something with the actual aria-label you want to use.

add_filter( 'generate_logo_output', 'tu_logo_target', 10, 3 );
function tu_logo_target( $output, $logo_url, $html_attr ) {
	printf(
		'<div class="site-logo">
			<a href="%1$s" title="%2$s" rel="home" aria-label="something"  rel="noopener">
				<img %3$s />
			</a>
		</div>',
		esc_url( apply_filters( 'generate_logo_href' , home_url( '/' ) ) ),
		esc_attr( apply_filters( 'generate_logo_title', get_bloginfo( 'name', 'display' ) ) ),
		$html_attr
	);
}

You can use one of the methods introduced here：
Adding PHP: https://docs.generatepress.com/article/adding-php/