Debian is a free operating system (OS) for your computer. An operating system is the set of basic programs and utilities that make your computer run. Debian provides more than a pure OS: it comes with over 59000 packages, precompiled software bundled up in a nice format for easy installation on your machine.
Try seeing if your monitor has any weird power settings. I’d imagine it’s not a monitor problem, based on it turning back on after mouse movement, but perhaps it improperly responds to some message sent over the cable.
Speaking of that, what cable are you using? Is it HDMI or Displayport, and does the laptop have a full port or are you using a USB adapter?
I am using the HDMI port on a USBC port replicator / Dock (so that there is only one cable connected to the laptop)
This sounds like a power saving activity, which might not be caused by the OS, check your BIOS too.
I did not have this issue when only using the laptop's display, and in fact the laptop display does not blank.
The power saving might be the port powering down, not the display.
The issue seems to have been resolved?? It has stopped blanking except sometimes when I am logged out. I come back in the room to see it blanked, and then lights back up on its own. Stranger and Stranger.