To do Alt + P P G on Mac in Excel, download and install Accelerator Keys, then press Option, followed by P, P, and G.
Command: Print Gridlines
This is how to do Alt + P P G on Mac in Excel with Accelerator Keys, the native ribbon and alt key shortcut solution for Mac users who get more done with Excel.
Alt + P P G toggles whether gridlines are included when printing your worksheet. By default, gridlines don’t print. Enable this option when you want the cell boundaries visible on your printed output.