Why is a product attribute missing from layered navigation in Magento 2.4.7?

I’m trying to understand how product attributes work with layered navigation in Magento 2.4.7.

I have a product attribute that I’d like customers to use as a filter on category pages, but it doesn’t appear in the layered navigation. The attribute is configured for use in product listings, so I’m wondering whether there are additional settings required for it to appear as a filter.

Which attribute settings should I check first, and how do the attribute’s filterable properties, product visibility, and catalog indexing affect whether it appears in layered navigation?

I’d appreciate a troubleshooting approach that helps identify the cause without unnecessarily changing the attribute configuration.