Aha! Just found out the easy way to make DDG my default homepage (it was G**gle). I'd already put DDG icon on my toolbar as a bookmark; simply drag-and-dropped it onto the 'reload home page' button (the wee 'house' icon) on the address bar.
Up pops a "Set Home Page" box, asking:
Do you want this document to be your new home page? Select 'yes' (obviously!)
Job done! No more Gggle, or whatever your homepage used to be.
(tried "about:config", and reset "keyword:url"; to what effect, I don't know (?)