I read the article and while I disagree on the advantage of 2.4 GHz vs 5 GHz (because of the absorption of 2.4GHz by the water in the leaves of the trees) I had a thought about where your outbuilding gets its power. Do the power lines run from your house, and if they do why not try Ethernet-over-power? I had originally used Powerline unites to bridge Ethernet from one end of my house to the other instead of running Cat. You just have to make sure that there are no transformers in the way, that it is a straight piece of copper wire from your circuit box to the outbuilding. You should get 1-2 Gbit/second out of it.
https://www.amazon.com/Powerline-Computer-Network-Adapters/b?ie=UTF8&node=1194444