Hi...
From what I understand, 802.11ac support in Linux is limited at the moment, which is why you weren't able to find much of anything in your searches. However, I did find
this adapter which offers 802.11ac support in Linux. You can also purchase it from Amazon
here. I'm not sure if it's supported out of the box, so you may need to compile and install the driver listed
here, although it only supports kernel versions 2.6.18 through 3.19.3. However, you can find a patched version of the driver for newer kernels along with additional information
here and
here. You can also run this command to see which kernel version you have...
You should also find out if your kernel supports 802.11ac.
Hope this helps...
Regards...