Laravel Logging to Slack Workbook causes "Curl error (code 3): <url> malformed"
env() will return null if the string is not defined in .env so you're just setting url to null. Perhaps you meant to do something like
'url' => 'https://hooks.slack.com/services/TC3S00...'Or
'url' => env(SLACK_URL, 'https://hooks.slack.com/services/TC3S00...')(and have an entry in .env for SLACK_URL)