Hello,

It is not possible to make the Related products full-width, provided you have set the full-height sidebar.

At the same time, we can change the product and make it full-width, please add this code to the product page settings https://prnt.sc/qfc9n4

body .product-image-summary-inner div.product-images{
display:none;
}
body .product-image-summary-inner div.entry-summary{
    flex: 0 0 100%;
    max-width: 100%;
}

Best Regards