About half of Notion's supported embed types are generic iframes. The rest either have edge cases, custom formatting, or use a third-party script to embed content.

YouTube

This is a caption

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Twitter

(uses the official Twitter embedding SDK)

https://twitter.com/emichan_iguana/status/1275210350665719810?s=20

Spotify Playlist

https://open.spotify.com/playlist/2MgkBl2rQnPdF3WZ6ciajc?si=YO7W88RIQbCdeQpEPsq0eg

Spotify Podcast

https://open.spotify.com/episode/1sTz31srankwiOvIhhjgA9

Spotify Podcast 2

https://open.spotify.com/episode/0Ok2HlpJ06C8c2Wrhm8Nkv

Spotify Preserve Scale

https://open.spotify.com/embed/track/2S2ASICVK0L1LtjaysKsel