Previews de vídeo não aparecem mais desde 3.2.0.beta3

[JammyDodger]

Isso foi levantado recentemente neste tópico de Support

Video thumbnails not generated for uploaded videos in Discourse forum

Does Discourse automatically generate video thumbnails for uploaded videos? By default, Discourse does not automatically generate video thumbnails for uploaded videos. However, the Insert Video (theme component) plugin does generate video thumbnails automatically. Is there a way to enable Discourse to automatically generate video thumbnails for uploaded videos by default? Note: The Insert Video (theme component) plugin currently only works with MP4 videos. Support for mov, ogg, webm videos is …

Acho que é uma mudança deste PR:

DEV: Prevent videos from preloading metadata