Mattshark89
  1. Open VRChat with the phone's auto-rotate setting turned off. The app should boot up into a portrait orientation.
  2. Once in a world, press the menu button to open your small menu.
  3. Open any quick menu item (Worlds, Avatars, etc.)
The app immediately flips to a Landscape Orientation. Once the menu is closed, it flips back to a Portrait orientation.
This may be an intended feature, but if so it feels very clunky and unintended.