Hello,

You can use the Theme’s Layout Builder to create Custom Layouts for the Single Product page > and in that Layout you can add the product grid or carousel widget in the bottom of the layout and choose the data source “Related Source” and enable the option “Hide out of Stock products”. You can find the Layouts under the Dashboard > Layouts.

Here is the Guide to that: https://xtemos.com/docs-topic/single-product-page-builder/

Best Regards.