Point all URLs to homepage but maintain URL

Add this code to the functions.php file of your (child) theme or as a plugin-

add_action( 'init', 'wpse_393237_add_any_endpoint' );

function wpse_393237_add_any_endpoint() {
    add_rewrite_endpoint( '.*', EP_ALL );
}

Please note, you may need to flush the rewrite rules if you see a 404 error. (simply saving the permalink does the trick)

Ref: https://developer.wordpress.org/reference/functions/add_rewrite_endpoint/