I have been given a slot loading iMac G3 266MHz with 64MB RAM and the original 6GB hard drive.
I always use debian unstable (sid) so I installed that for console mode only.
I only install X11 when I know everything works in console mode.
I installed X11, choosewm so I can choose which window manager to use, the flwm and fluxbox window managers because they are small and fast, and big-cursor because I like it.
Type 'startx' and I got the same black screen everybody gets... Oh good.
Half a day of hunting the internet brought no joy until I used the xorg wiki.
X11 looks in /usr/share/X11/xorg.conf.d for any interesting and unusual configuration files it might need.
All that was in there was 10-evdev.conf. Hmm.
I had an xorg.conf file I had downloaded from mac.linux.be earlier (obviously that didn't work!). I copied it into /usr/share/X11/xorg.conf.d/20-display.conf.
Then I edited the 20-display.conf file to remove everything apart from the Screen and Monitor sections.
I typed 'startx' and after a bit of a delay because 64MB RAM is not enough for a good X11 experience, the choosewm window came up, I chose flwm and it worked!
Obviously I have used assorted linux and BSD distributions over the years, but this sort of thing really really vexes me. I've downloaded the ppc version of debian unstable, they KNOW xorg.conf is gone, they KNOW iMacs will have a black screen and yet nothing is done about it! Vexing.