AC1200 Wireless Adapters

Discussion
Browse to https://wikidevi.com/wiki/Special:RunQuery/Wireless_adapter_query.

Find "Supported 802dot11 protocols:", enter abgn+ac.

Find "Table query type:", select linux_support.

Click "Run query".

Scroll down to find a table of known abgn+ac Wireless Adapters with chipset, pciid, and possible linux driver. The AC1200 adapters in the table will have RTL8812AU or BCM43526 chipsets. The other chipsets listed support other protocols.

Driver Locations
8812au is available at https://github.com/gnab/rtl8812au. Download and extract the zip file, cd to the extracted directory (/path/to/rtl8812au-master), follow the instructions provided in README.md.

wl 6 is in portage as broadcomm-sta, but support of bcm4352 and bcm43526 is very unlikely. The BCM43526 is not in the supported device list at http://www.broadcom.com/docs/linux_sta/README_6.30.223.248.txt. Using ndiswrapper and windows files may work. As the BCM43526 adapters are usb2.0, 480 mbps, they should be unable to support the theoretical 867 mbps of the 5 ghz channels.