Update 02/14/2022: After an update to macOS version 12.2.1, the USB-C ports can output a 4k@120Hz signal using a USB-C to DisplayPort dongle.
The two USB-C ports support Thunderbolt 3 (up to 40Gbps), DisplayPort, charging, USB 4 (up to 40Gbps), and USB 3.2 Gen 2 (up to 10Gbps). The M1 SoC is limited to one external video output, up to 6k @ 60Hz, or 4k@120Hz using a USB-C to DisplayPort dongle. Some users have shown that it's possible to connect more than one external display using a third-party dock that supports Displaylink, though we can't confirm this. There are no USB-A ports, so you'll likely need dongles for your peripherals.
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