Exclude logo (desktop and mobile) from lazy load in GeneratePress theme with Perfmatters plugin. Source: https://perfmatters.io/docs/lazy-load-wordpress/ *Update* This is no longer needed as you can add class exclusions in Perfmatters.

exclude-logo-lazy-load-generatepress.php

//add no-lazy class to primary logo
function wpd_generate_logo_output($output, $logo_url, $html_attr) {
  
  //add our no-lazy class
  $html_attr = str_replace('class="', 'class="no-lazy ', $html_attr);
  
  //logo output
  printf(
	'<div class="site-logo no-lazy">
		<a href="%1$s" title="%2$s" rel="home">
			<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
  );
}
add_filter('generate_logo_output', 'wpd_generate_logo_output', 10, 3);

//add no-lazy class to mobile header logo
function wpd_generate_mobile_header_logo_output($output) {
  
  //make sure we can get default settings
  if(!function_exists('generate_menu_plus_get_defaults')) {
	return $output;
  }

  //get settings args
  $settings = wp_parse_args(
	get_option('generate_menu_plus_settings', array()),
	generate_menu_plus_get_defaults()
  );

  //logo output
  return sprintf(
	'<div class="site-logo mobile-header-logo">
		<a href="%1$s" title="%2$s" rel="home">
			<img src="%3$s" class="no-lazy" alt="%4$s" />
		</a>
	</div>',
	esc_url(apply_filters('generate_logo_href' , home_url('/'))),
	esc_attr(apply_filters('generate_logo_title', get_bloginfo('name', 'display'))),
	esc_url(apply_filters('generate_mobile_header_logo', $settings['mobile_header_logo'])),
	esc_attr(apply_filters('generate_logo_title', get_bloginfo('name', 'display')))
  );
}
add_filter('generate_mobile_header_logo_output', 'wpd_generate_mobile_header_logo_output');