I have enable the option to "Flash screen when an alert sound occurs" under Accessibility setting in System Preferences.
It works successfully with many apps such as Microsoft Outlook but not with Slack. How can I get the screen to flash when I receive a Slack notification?
Further information:
It looks like Slack uses the native notification interface as you can control the notification type under the Notification Centre settings:
Best Answer
From an email with Slack support:
This was written on the 16th May 2019. Slack v3.3.8