SVG logo alt text request

but if you like to force : open that svg file before uploading with a (good) text editor and insert on the svg tag yourself an alt attribute.

if you like to have on the a tag ( this is not an attribute allowed for a-tag ) a title or alt:
( see https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a )

function custom_logo_attriubtes(){
?>
<script>
(function($){
  $('.logo > a').attr({ title:"here comes a new title Attribute", alt:"Your new Alt Attribute" });
})(jQuery);
</script>
<?php
}
add_action('wp_footer', 'custom_logo_attriubtes');