I recently built a Mac app that enables these alt-shortcuts in Mac Excel. You can download it at https://www.acceleratorkeys.com.
Edit: Noted that the original answer was a little short. I was trying to avoid being overly promotional. If you download the app, you'll find that Excel alt-key shortcuts work exactly as they do on Windows. It works on macOS Catalina, and across Office 2016, 2019 and 365.
- Open Accelerator Keys.
- Open Excel.
- Hit Alt and use the shortcuts.
We're being used by consultants, investment bankers, financial analysts, accountants etc. I built this using Catalina's new accessibility features to control Excel and re-create the alt-key shortcuts on Mac.