External display black on wake when built-in display is disconnected

[toobuntu]

When "Disconnect the built-in display when an external display is connected" is enabled, waking from sleep leaves the external display black with only the mouse pointer visible. The built-in remains off as expected. Physically unplugging and replugging the external display restores it.

The kernel log shows the external display going through two link negotiations on wake. The first lands in RGB 4:4:4 8bpc; the HDCP subsystem then resets the link (abortHDCPNegotiation 0xe00002eb) and the second negotiation lands in YCbCr 4:4:4 10bpc due to the monitor's defective EDID advertising YCbCr support. The black screen may be the display stuck between these two negotiation phases.

Env:
BetterDisplay 4.1.5
macOS 26.3
Connection: MacBook Air M2 (2022) (Mac14,2) USB-C → Anker AK-A8176011 passive USB-C to HDMI cable → DELL SP2309W HDMI input.

[waydabber]

Hmm. I am not really sure what could be the problem. You can try configuring the app to automatically reinitialize the display on wake and/or configure a color mode with Configuration Protection, maybe that helps if this causes the issue.