curl --request GET \
  --url https://discord.com/api/v10/stage-instances/{channel_id} \
  --header 'Authorization: <api-key>'

{
  "guild_id": "<string>",
  "channel_id": "<string>",
  "topic": "<string>",
  "privacy_level": 123,
  "id": "<string>",
  "discoverable_disabled": true,
  "guild_scheduled_event_id": "<unknown>"
}