MacBooks with an Apple M1 processor can handle only one external monitor, but the OWC USB-C Dual HDMI 4K Display Adapter with DisplayLink doubles the number.
OWC USB-C to Dual HDMI 4K Display Adapter with DISPLAYLINK for Apple M1 Mac or Any Mac or PC with USB-C or Thunderbolt : Electronics
CableCreation Thunderbolt 3 to Dual HDMI Display, Thunderbolt 3 to Two HDMI Adapter, 4K@60Hz, 40Gbps, USB C to HDMI Cable Compatible with Mac and Some Windows Systems : Electronics
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i-tec USB C Dual 4K HDMI Video Adapter Works with Mac [macOS, MacBook Pro](1x 4K) and Windows/Linux/Ubuntu (2X 4K) USB C to Dual HDMI Monitor, DisplayLink, MacOS Extend Mode HDMI Converter
OWC USB-C Dual HDMI 4K Display Adapter with DisplayLink
j5create 8K USB Type C to Dual HDMI Display Adapter - Single 8K60/4K144 or Dual 4K60 - Support MST Extended Mode, for Gamers and Professionals, Suitable for Windows Laptop (JCA465)
OWC USB-C Dual HDMI 4K Display Adapter
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OWC USB-C to Dual HDMI 4K Display Adapter with DISPLAYLINK for Apple M1 Mac or Any Mac or PC with USB-C or Thunderbolt : Electronics
OWC USB-C Dual HDMI 4K Display Adapter with DisplayLink
USB-C Dual HDMI 4K Docking Station with 100W PD Pass-Thru
This USB to dual DisplayPort adapter lets you add two 4K 60Hz DisplayPort monitors to your Windows or Mac computer. Create a dual-4K 60Hz workstation The adapter lets you use a single USB 3.0 port on your laptop to output dual 4K resolution at 60Hz to two independent displays. Simply plug the adapter into a USB 3.0 (5Gbps) port on your Windows or Mac system and connect your DisplayPort monitors to the adapter.
StarTech.com USB 3.0 to Dual DisplayPort Adapter - 4K 60Hz
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i-tec USB C Dual 4K HDMI Video Adapter Works with Mac [macOS, MacBook Pro](1x 4K) and Windows/Linux/Ubuntu (2X 4K) USB C to Dual HDMI Monitor, DisplayLink, MacOS Extend Mode HDMI Converter