Plugin used in theme

[Falco]

That is not a plugin but a theme-component:

Topic List Thumbnails

Summary Topic List Thumbnails allows you to show topic thumbnails in topic list views. Preview Theme category - Discourse Meta Repository Link https://github.com/discourse/discourse-topic-thumbnails New to Discourse Themes? Beginner’s guide to using Discourse Themes Install this theme component Optimized images are generated for the lists, and different resolutions are made available for high-dpi displays. Images ar…