The fast2704 wifi doesn't have an 802.11n feature

On fast2704n, lede's wifi feature is 802.11 bg, no n, and it doesn't work with all the drives of lede, hoping someone will help.
Wifi is bcm43217, which supports 802.11bgn.

BCM43217 is only supported (partially) by b43. While b43 has some very basic support for newer devices (n_phy), it doesn't not support HT rates (anything >54MBit/s) nor 5 GHz operations - and it most likely never will.

I have a bcm43217 driver in asus rt-ac1200g +, but he appears to be binary, and I'm not going to transplant it.