That's bad news. I tested in Firefox and Edge (and Samsung for Android). Do you mean all keys or just the arrows? I offered alternatives to arrows, as you can see if you hover over the buttons.
Nothing at all. Furthermore, input buffer not being processed, when I click Back to get here, there comes the cursor keys and RMBs I did in the game. This on Win10, tho, I had other keyboard issues, probably hardware/driver related. So maybe I'm the only one.