There is an API route to do this if you know your way around a REST API.

POST /api/v1/archive/convert-twitch-live-chat

with the following JSON body

{
  "live_chat_path": "/data/temp/path-to-your-chat.json",
  "channel_name": "TwitchChannelName",
  "video_id": "acf3c6fb-5f2b-11f0-bb1d-0e78a72ec63e",
  "video_external_id": "123456",
  "channel_id": 85498365,
  "previous_video_id": "123456",
  "first_message_epoch": "1752330167621000"
}

• live chat path: the path to the chat-downloader file from the container's perspective, so place this in the temp directory
• channel_name: name of the name
• video_id: Ganymede ID of the video (you can supply a random one)
• video_external_id: the Twitch video ID if you know it, else random
• channel_id: the Twitch channel ID, you can find this in the chat file I believe, or TwitchDownloader chats
• previous_video_id: a previous Twitch video ID of the channel, you can put whatever here
• first_message_epoch: The first message timestamp in epoch format (microsecond format) you'll need to find the first comment and convert to epoch

The output path will be

outPath := fmt.Sprintf("%s/%s-chat-convert.json", envConfig.TempDir, body.VideoID)

So typically /data/temp/<VIDEO_ID>-chat-convert.json. Then you can run the resulting JSON file through TwitchDownloaderCLI chatupdate to populate emotes,

The API route requires authentication. Use the cookies from your browser session or log in with the API and use the cookie for the above POST request.

POST /api/v1/auth/login

{
  "username": "admin",
  "password": "ganymede"
}