M4 Mac won’t detect second 4K monitor when both support >144Hz (only works after toggling DisplayPort version)

Summary

When connecting two 4K high-refresh-rate monitors to an M4 Mac using USB-C → DisplayPort cables, only the monitor connected first recieves signal.

Setup

Mac models tested: 2x M4 MacBook Airs (including a factory-new unit) and M4 MacBook Pro

Monitors tested: Samsung Odyssey G81SF and KTC M27P6 (both support refresh rates above 144Hz)

Cables tested: USB-C → DisplayPort 1.4; also tested one USB-C → HDMI 2.0

MacOS versions tested: Sequoia & Tahoe 26.0.1

Problem

When both monitors are connected, only the first one receives a signal.

The second monitor stays dark, no matter what refresh rate is set in System Settings > Displays.

I'd like to run both at 4K 120Hz, but the issue happens even at 30hz and 60hz.

Workaround

Using the Odyssey’s on-screen display menu, if I temporarily set its DisplayPort version to 1.1, both monitors connect successfully, and the Odyssey is capped at 30Hz. If I then switch the Odyssey’s DisplayPort version back to 1.4, both monitors remain connected, and I can set the Odyssey to 120Hz as intended. Unfortunately, I have to repeat this DisplayPort version toggle every time I reconnect the monitors or restart the Mac.

When using one HDMI cable instead, temporarily setting the monitor’s HDMI version to 1.4 and then switching it back to 2.0 also allows both monitors to connect successfully.

Question

Is there a way to connect two 4K monitors that support >144Hz to an M4 Mac and use them at 120Hz without having to change the DisplayPort version each time?