I'd like my posts to display the date that they were last updated, rather than the original publication date. How can I do this?
unfortunately Uku doesn't support this. You'd need to implement this by yourself. Maybe you can use a plugin to insert this information somewhere.
I strongly recommend using a child theme for direct code adjustments. A prepared child theme folder is linked in the Uku documentation.
Please understand that we cannot provide help for individual customizations.