To change read more link in blog page to external url.
#1. First, on each blog post > Click 3 dots > Click Settings
#2. Enter External URL in Source URL
#3. Final, use this code to Code Injection > Footer
You can also use this free blog tool so you can customize blog easier without using code.
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script>
<script>
jQuery(document).ready(function(){jQuery(".blog-basic-grid--container").each(function(){var a=jQuery(this),b=a.find(".blog-title a").attr("href"),c=a.find(".blog-more-link");b&&c.length&&jQuery.ajax({url:b+"?format=json",dataType:"json",success:function(d){if(d.item&&d.item.sourceUrl){c.attr("href",d.item.sourceUrl).attr("target","_blank")}},error:function(){console.log("Error: "+b)}})})});
</script>
