SparroHawc wrote:
This is a common issue with cheap keyboards. You don't necessarily have to bind L and R to the same key - you just have to bind them to keys that don't conflict with each other. Try using homerow keys (ASDFJKL) as most keyboards will allow you to press these simultaneously. Barring that, try binding one or more of the keys to 'modifier' keys - SHIFT, CTRL, et cetera.
this is really the easiest work around other than buying a cheap controller. When i was on macos, I'd set L/R to command and option for that part. after that though I got a Macally ishock controller for 14 dollars and just used a pad. it's the closest thing I found to a snes pad and very similar to a dual analog stick from sony. Any controller that supports HID plug and play will work though.