Yeah sorry, I was only counting engines suitable for DDG, ie. English language etc. There's also Qwant and although they are crawling their results still appear to be Bing.
Their only options are Google, Bing, Yandex, Exalead, Gigablast, and Mojeek, and most probably in that order as the last two need to grow considerably first. Unless there's any others that have their own index?
Although they just show Bing results for me so don't know how much of their own index is actually used.