Want to know when a torrent has finished downloading on qBittorrent? You can trigger custom .sh scripts to do that!
In Tools > Options > Downloads > Run External Program I use a script on Torrent Finished. You'll need ./torrentslack.sh %N add an executable bash script in a location qBittorrent can access, which is important if run in a Docker Container. The %N attribute denotes the torrent name, within qBittorent it shows other options that can be accessed too.
Below you'll find a sample script, which uses the classic Slack Webhook app.
#!/bin/bash
TORRENT_NAME="$1"
WEBHOOK_URL="{{SLACK_WEBOOK}}"
curl -X POST -H 'Content-type: application/json' --data "{
\"text\": \"Download complete: $TORRENT_NAME\"
}" "$WEBHOOK_URL"