iMac Pro (5K screen, Radeon Pro Vega 64, 8 core Intel Xeon W)
Short description of error
Exact steps for others to reproduce the error
Launch on iMac Pro, and you'll see that Blender takes up only a portion of the window and all controls are offset, so to click on a menu, you have to click at the top of the window, not where they are actually displayed. See attached image.