Does video out of the HDMI port or the Thunderbolt 3 ports come from the included Radeon 580 or from your computer's dGPU or iGPU?

They say you can connect an LG UltraFine 5K display to the Blackmagic eGPU but how is this any different than any other Thunderbolt 3 device with two Thunderbolt 3 ports?

Blackmagic eGPU

Blackmagic eGPU

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