Xianxia is originally born out of wuxia so modern wuxia would be a good approximation of what they'd look like. The most famous writers in this genre are Gu Long and Jin Yong, and their books are some of the earliest translated titles out there. Moreover, their books are some of the most popular and famous works in Chinese literature; with other books namedropping them all the time. But despite all this, they're barely ever mentioned on NUF; even when people are discussing wuxia novels. The only reasonable conclusion for this is that readers on NU just don't care about them so there's no reason for translators to tackle similar works.