I have a MacBook Pro with an M3 chip. I also have a Belkin Thunderbolt 3 hub with 2 monitors. My older MacBook Pro recognizes the two external monitors, but the M3 MacBook Pro only sees one. Notice that it ONLY SEES ONE external monitor, as opposed to seeing two mirrored monitors.
MacBook Pro 17″, macOS 10.13
If you have this MacBook Pro it supports only one external display:
MacBook Pro (14-inch, M3, Nov 2023) - Technical Specifications - Apple Support
If you have this MacBook Pro it supports only one external display:
MacBook Pro (14-inch, M3, Nov 2023) - Technical Specifications - Apple Support
Display interfaces are generated deep inside the system on a chip. How many there are depends on the exact type of Processor:
With one minor exception, the same rules we learned for the M1 and M2 still apply to the M3 models. M3 (plain) like the 13-in and 15-in supports up to ONE External fully hardware-accelerated external display. Except the M3 MacBook Air models with 13 or 15-in display, which can support a second external display instead of the built-in display when you close the cover on the built-in display.
M3 PRO processor supports up to Two fully hardware-accelerated external displays.
M3 MAX processor supports up to Four fully hardware-accelerated external displays.
MacBook Pro w/ M3 chip not recognizing multiple external monitors
