Both Friendica and Pleroma seem to have the same problem that video files are loaded the moment they appear in your timeline(*), whether you click play or not. And both are completely ignoring the provided cover image. Mastodon does this much nicer, showing the cover image, the actual PeerTube channel account, and only loading the video in an embedded player after you click to do so.

(*) I know, because when I'm browsing on cellular data I'm almost immediately out of my data bundle if a PeerTube video post appears in my Friendica timeline.