Editing Basic Debian Installation (section)

== Non-Free Drivers ==
Debian's militant policy towards non-free drivers can be rather annoying.  The Radeon built-in graphics controller on the motherboard for lamppost (ASUS M4A785-M) apparently needs some 'non-free' firmware, which is not detected during the install process, even though I'm using the non-free firmware installation disk image.  Because the firmmware is not loaded during the install, it isn't included in the initramdisk, and therefore the device is loaded in an inoperative state.  There is a firmware package available to install:
 apt install firmware-amd-graphics
... but even after rebooting it doesn't load because by the time the root filesystem is mounted, the devices are already initialized.  Until I find a better way, the device needs to be unloaded and reloaded after boot to enable the graphics
 rmmod radeon
 modprobe radeon

Similarly, some RealTek drivers need to be added:
 apt install firmware-realtek

Some systems also require tigon/tg3 drivers.  This one installs more than a few other packages, too ... including the amd-graphics package mentioned above.
 apt install -y firmware-linux-nonfree