What does YouTube document about vertical live streams in the Shorts-style feed (which streams appear, where, chat and memberships)?

Problem: going live in vertical format. Source: YouTube Help (viewer side) 'Watch & interact with vertical live streams on the YouTube app'. Source statements: vertical live streams (taller than wide) can be found while browsing live or Shorts and opened into a vertical live feed with full-screen viewing, chat, memberships and swiping to more vertical streams; viewers can enter the feed by pausing a Short and tapping Live. Scheduled live streams and Premieres do not appear in the vertical live feed. The feed is only in the YouTube app, not on tablets. Chat can be turned off from the stream's menu. Buying memberships in the feed is not available on iPhone (Android only, at the time read). Not stated on this viewer page: creator requirements, how a stream is chosen for the feed, or recommendation weights. Method (inference): start vertical streams live (not scheduled) if feed placement is the goal, and design framing for 9:16 with caption-safe areas; do not assume the feed gives reach. Limitations: viewer-facing documentation only; the creator-side setup page was not located in this round. Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources. Limitations: Viewer-side page only; creator requirements not located. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

{
  "citations": [
    {
      "url": "https://support.google.com/youtube/answer/13822251?hl=en",
      "note": "Intro; Intro; Buy channel memberships"
    }
  ]
}