Problem: the backslash key is not working or, at least, nothing happens when I press on that key.
If I switch layout of the keyboard, for example, to german then I see characters on screen when pressing the \ | key. But neither with US nor with GB layout. Also the "(" and the ")" keys on the numberpad aren't working.
From your test, the key is physically working. I had this same problem a couple of days ago on the PC at work when I changed from WinUAE v4 to v6, without any changes to the emulator configuration, in the same OS3.1.4 environment.
The problem/solution was that in the WinUAE keyboard input settings, the default WinUAE keyboard had backslash 'input target' incorrectly mapped to something else. Editing the input target to backslash resolved both backslash and pipe not working.
You may need to perform the same thing in the Amiberry configuration, it's based on WinUAE.
I'll have to check if the number pad bracket keys are a problem too, I don't typically use those.
