Isn't it the kernel itself (perhaps the GPU driver) that should detect keyboard activity and turn on the signal to the monitor to make the text console visible?  Or, is there a userspace process involved with that?

Motherboard is an Asus Pro WS X570-ACE.  CPU is an AMD Ryzen 7 5800X 8-core.  GPU chipset is Navi 14 [Radeon RS 5500/5500M / Pro 5500M].  One physical monitor is on an HDMI port via a Kopul HDMI switcher.  The other physical monitor is on DisplayPort.  Current kernel is 6.12.101+deb13-amd64, but symptoms happened with 1 or 2 earlier Excalibur kernels.

The system serves as a droid control ship for VNC sessions with diskless zero/thin-client display heads that boot via PXE.

Normally overnight, I push the power-off buttons on the physical monitors to save energy.  At least with earlier Devuan releases, if the monitors are left on and the system tries to blank and power down the monitors, the monitors will unblank and turn on later during the night.  I use "setterm --blank 0 --powerdown 0" to keep the system from trying to blank and power down the monitors.

The problematic sequence is

1. The physical monitors are powered off to save energy.

2. Someone starts one of the diskless machines and launches a VNC session.

3. I push the power buttons on the physical monitors.  After showing the manufacturer's logo for several seconds, the monitors report no signal and go into standby state.

4. I tap on the keyboard to try to wake up the monitors (or keep them awake).  At this point, Num Lock, Scroll Lock, and Caps Lock turn on/off the respective LEDs.  As an experiment, I once logged in blindly, and the monitors did not display anything at that time.

5. Immediately after the VNC session is terminated, the monitors come out of standby state and show the results of the blind login and a couple of commands that had been done blindly.

Any suggestions for getting the GPU to send signal to the physical monitors so they will power up and display stuff?

Thanks!