Running on a Mac mini (2018) with "Graphics Card: Intel(R) UHD Graphics 630" , not happy also, SL Viewer ( the viewer with better experience I tested among all others) is just frying the box ( even using low graphic config ).
Mac Mini "Apple store GLView app" says it fully supports OpenGL till version 4.1 and OpenCL 1.2 ( Not sure if SL uses that one).
But latest SL viewer version "Second Life Release 6.4.3.542964 (64bit)" uses "OpenGL Version: 2.1 INTEL-14.6.18".
To me looks like a modern software, using OLD graphic libs version, not sure why, and also not sure if making it to use new 4.1 GL version would make things better under MacOS+SL .