When booting my PowerBook Aluminum G4, I get a pop-up screen that says "The system is running in low-graphicsÂ mode. Your screen, graphics card, and input device settings could not be detected correctly. You will need to configure these yourself." This is a big-endian 74xx CPU. The lscpu command says it is a PowerBook5,6 model.
This problem has been bisected to commit 31bfdb036f12 ("powerpc: Use instruction emulation infrastructure to handle alignment faults"). I am confident of the accuracy of the bisection.
Attached is the configuration.