Availability of Excel Dynamic Arrays
As stated on the course landing page, Dynamic Arrays are currently generally available in OFFICE 365 Monthly Update Channel.
As of November 2019 they are ALSO available on Excel for the Web.
If you have an Office 365 subscription but are on the semi-annual update channel, you can switch to the monthly update channel or test the new functions by using Excel on the Web. Just login to your Microsoft Account and open Excel on the browser.
If you're part of an organization and aren't sure which update channel you're on, please ask your IT about Office update Frequency.
Here is more information on how to get the newest features.
Dynamic Arrays will not be part of Excel 2019 perpetual license.