This page is for those of you unlucky people, who after installing a Debian sid with a desktop leads to a black screen.
My experience is that some Apple laptops have difficult video cards, which cannot be properly read by the kernel in the so called kernel modesetting. This is due to my opinion about the missing BIOS that normally would give info about the card.
It is not widely known that G4 Titanium PowerBooks, which end up with a black screen, can still have a graphical user interface by connecting the machine to an external monitor. A user reported that she had to go back to LightDM as display manager. This could be a solution for people having trouble to get a desktop on their Apple laptops.
Some people reported a black screen on PowerMac G5 with a non-flashed Radeon card, designed for PC’s. The trick here is to boot from open firmware with the stock NVIDIA GeForce 6600 and switch to the the Radeon card in Linux. To have 3D acceleration working in the Radeon card one has to use an xorg.conf file. For details see here.
If you still don’t know what to do you can go to the MintPPC forum or ask help in the PowerPC section of Macrumors forums.