What layout uses ^? for backspace? The wikipedia[w] page doesn't appear to be aware of it, and a few simple searches turned up nothing...

I suppose you mean, "I can't backspace with my backspace key" -- as you probably can backspace fine with ^h (ctrl+h)?

[w] https://en.wikipedia.org/wiki/Backspace

It's just a matter of misconfigured terminal databases. I wrote some years ago a Linux Mini-HOWTO about it, I wonder where it is now...