I’m one of those who was thinking discreet GPU would provide much better performance. When watching Apple’s transition to Apple Silicon, I asked myself about discreet GPU options in future Macs. This article goes on to report that not only integrated GPU (thanks to SoC) will be faster, it could be easier to support and help Apple reduce costs. Apple never offered discreet GPU in iPad Pro. Why would it be different with Apple Silicon-based Mac? Will future Mac support external GPU? Probably but performance gain will be marginal.

ARM Mac graphics performance could beat discrete GPUs - 9to5Mac