私のセルフホスト環境は他のサイトほど「速く」ない

[Architect]

Few supported platforms that integrate with discourse are brightcove, youtube and Vimeo:

Handling uploaded videos

Discourse does integrate with various video providers, notably: brightcove via this plugin and youtube and vimeo. So if video is your Jazz we recommend you store them on one of those providers and use oneboxes.