Triangle shaped display glitches in Illustrator on macOS

Hi there,

Sorry to hear about this issue. I would like to know if turning off GPU worked for you, or the issue still persists.
Kindly update the discussion if you still need assistance with it.

Thanks,
Srishti

Gracie,

Ctrl/Cmd+E toggels between GPU and CPU (you can untoggle CPU if it fails to help).

This is what GPU is about:
https://helpx.adobe.com/illustrator/kb/gpu-performance-preview-improvements.html

Or, with this exquisite wording by Monika:

https://community.adobe.com/t5/illustrator/cpu-gpu-preview-modes-in-illustrator/m-p/10847674#M161071

Graphics cards are included in the system requirements:
https://helpx.adobe.com/illustrator/system-requirements.html

Apart from an inadequate card, the issue can be caused by lack of driver updating, lack of proper recognition of the card by the computer, and whatnot (including rifts in the space time, moon, weather, and the fact that Illy sometimes moves in mysterious ways).

Here are a few more pages about GPU troubleshooting:
https://helpx.adobe.com/illustrator/kb/gpu-performance-errors-troubleshooting-workarounds.html
https://helpx.adobe.com/illustrator/kb/illustrator-gpu-performance-driver-update.html