Having issues with Unreal 4.26.1 and 2019 iMac

I’m learning Unreal Engine lately and working through tutorials, learning paths and Unreal for Virtual Production. I’ve been working through a landscape building tutorial and a few things happen:

  1. the landscape maps go completely wonky at random. The landscape I am working on suddenly looks like a shattered glass all over my screen.
  2. when using certain Blueprint brushes, the engine will crash. Repeatedly. Specifically BP_Landmass_Brush & BP_MasterRiver.

I have a pretty decent machine:

MacOS Big Sur 11.2, 8-Core i9 3.6GHz, 64GB DDR4, Radeon Pro Vega 48 8GB HBM2.

I will literally turn off every application and have only Epic Launcher and Unreal Engine running. So I don’t get what the issue is. Is Unreal ONLY happy running on a Windows or Linux box?