I'm trying to track down some specific behaviour and it seems that every chipset handles Graphics Controller register 0x05 bit 6 differently, but at the same time the two I've tested have absolutely not enabled 8bpp mode (EDIT: One might have.), whereas every emulator I've tested has done so - despite the fact that the correct place to do this is in the Attribute Controller, not in the Graphics Controller.

Here's a test program to run in debug in DOS. Please type this in and see what you get.
EDIT: I forgot the "int 3" - this shows the register dump that wasn't showing when others tested it, oops.

a100
mov ax,12
int 10
mov dx,3ce
mov ax,4005
out dx,ax
int 3

g=100

In theory, you should get something like this (tested in a custom build of 86Box while I rework the VGA rendering stuff):

I get something very similar to this on my Intel GMA 4500MHD (2008). But my AMD Stoney Ridge (2016) gives something similar to but different from an emulator which seems to think that this means "enable 8bpp mode" (specifically QEMU 8.1.1, but IIRC DOSBox-X gives very similar output):

If you have something which behaves similarly to either of those I'd like to know, and if you have something which behaves differently from both I'd also like to see photos or something.