There are several new things I learned.
1) there is an oembed standard, an open protocol of how to embed media on one service in other website. #PeerTube supports oembed 👍
4) To setup oembed properly in #Drupal, you need a separate domain just for serving oembed media. It is for security reasons: to avoid sharing cookie space with the website.
Štěpán Škorpil's personal Mastodon server - instance of federated social network