Single Cat gives authors a compact dropdown when a content model needs exactly one category. Keep the relationship native to Craft without presenting a full element selector for a small, deliberate choice.
Choose the category group for the field and present its categories in a dropdown. Authors get a quick, familiar control with no ambiguity about selecting several values.
The selected value remains a Craft category element, ready for its title, URL, custom fields, and normal Twig, GraphQL and element-query behaviour.
Available for Craft 4 and 5. Get it from the plugin store.