This theme component will help you to filter the topics by its status “open” or “closed”. It will add a dropdown filter next to the existing categories and tags dropdown. You can limit this component to particular categories using the theme setting enabled categories. Else it will be displayed in all the categories. Also you can translate the texts.

Repository link :
https://github.com/discourse/discourse-topic-status-filter

Preview in Theme Creator

topic-status-filter: 690x364

https://meta.discourse.org/t/how-do-i-install-a-theme-or-theme-component/63682