Thanks for asking.
Because this will require change in code, I suggest you to setup child theme. You can refer following resource to learn more about installing child theme and best practices. Also sharing link using which you can download child theme:
Next, you need to copy few codes from content.php into child theme function.php file. You can find content.php file under /wp-content/themes/x/framework/functions/global/. Copy the code from line number 71 that says
// Excerpt More String to line number 91 i.e.
endif; and paste it into child theme function.php file. Then you can replace Read More in second return statement as per your requirement.