Blender on a macbook pro 2015 Catalina with Intel Iris pro and external Monitor bad performance

Blender 2.8.2 performance is very bad with an external Monitor - the basic cube stutters when moving. With the internal Monitor it is ok, with blender 2.97 it is ok. So it seems to have something to to with open CL support. Any suggestions what I can do without buying a Windows PC? I am asking for my Son who loves blender and who loves his Mac. thanks for help


Intel Iris is ok only for very basic works.
Get eGPU (Radeon Vega 56/64) and connect external monitor to it.
For GPU rendering look at OctaneX. It will be probably available tomorrow (17.07):

as I understand, eGPUs need support of open CL, which blender stopped since version 2.8 (but I am not sure).Does anybody successfully use a mac with an eGPU and blender newer than 2.8?