Late 2020 models of MacBook Air, MacBook Pro 13-inch, and Mac Mini systems using the original Apple M1 or 2022 models of MacBook Air, and MacBook Pro using the Apple M2 chip support only a single external display over the Thunderbolt 3 ports, even when connected to a Thunderbolt 3 docking station or adapter with more than one video output. This limitation also applies to using multiple Thunderbolt or USB Type-C display adapters on both Thunderbolt/USB Type-C ports.
This is not a limitation of StarTech.com products specifically, and Apple lists support for only one external display in the Tech Specs for Video Support on the M1 MacBook Pro 13” [external link to apple.com]. Turning off the laptop display or using clamshell mode does not change this.
One option that allows for more than one external display with an Apple M1 or M2 silicon is to use a USB-C DisplayLink-based docking station or video adapter that requires a driver install. One dual monitor example is our DK30CHDDPPD, but please contact StarTech.com support for a recommendation based on your specific setup.
Please note: this single monitor limitation does not affect Intel-based Macs with Thunderbolt 3, or later M1 models that ship with M1 Max, M1 Pro, or M1 Ultra processors.