I've installed debian pocketworkstation on my SD card on my SL-5500. It also has running OZ/GPE 3.5.3.
Some strange things have occured to GPE as time has passed after installing debian. The ctrl-c used to work on the software keyboard to terminate apps in the console, but now it opens the calender. The hardware keyboard does absolutely nothing in GPE, so I have to use the software one exclusively. The only hardware key that has any response in GPE is the on/off cancel button, which I am glad is working correctly to suspend the PDA.
The debian environment, which I run from a terminal window in GPE is able to use the hardware keyboard flawlessly, as well as the on/off button, the arrow keys, etc.
The problem started after debian froze one time and I had to do a hard reset (battery replace switch).
I don't mind about not having keyboard in GPE because right now I only use it to get into debian, but I hope in the future to boot to just an OZ console and start debian from there, not loading GPE at all, and I'm worried that I'll figure out how to get it to boot to the console but I won't be able to log in or anything because the keyboard won't work. (speaking of which, if anyone knows how to exit GPE to a console that would be helpful).