“Designed by” is a big red flag
It’s generally not a good idea for a web designer to put a “designed by” link in the footer of websites that they create, and they usually know it too.
The main reason is Google; putting that link down there will hurt the site that it’s on. It’s a tiny amount, but it’ll still hurt. If you’ve developed a site to help a company, why would you do literally anything that actively hurts it?