macOS Tahoe 26.1 – USB-C→DisplayPort goes black on Samsung Odyssey unless Game Mode is ON

[jadraker]

Setup

• MacBook Pro 2023 (Apple Silicon), macOS Tahoe 26.1 (clean install)
• Monitor: Samsung Odyssey via USB-C→DisplayPort
• HDMI→HDMI from the Mac works fine

Symptoms

• In the monitor’s Normal profile, it works at first but after a while (sometimes after sleep/restart, sometimes randomly) it fails.
• When it fails, the panel is black and macOS doesn’t detect the display at all.
• Switching the monitor to Game Mode is detected immediately and video returns; switching back to Normal breaks it again.

Tried

• Different USB-C ports
• Option → Detect Displays
• Toggle DP 1.4 ↔ 1.2, FreeSync/VRR OFF, HDR OFF, MST OFF
• Clear display prefs & NVRAM
• Clean macOS install
• Note: the same USB-C→DP cable outputs video from an iPhone 17 to this monitor.

Questions

1. Is this a known Tahoe 26.x DP/EDID handshake issue?
2. Any stable OSD combo for Odyssey Normal mode (DP version / VRR / HDR) to prevent the dropouts?
3. Is there a fix in newer 26.x builds?