I’m still determined. Is there a libre solution for 802.11ac 5 GHz Wi-Fi? Well, well, if you ask like that, there is a compromise you can make. You can make use of so-called “Wi-Fi repeaters” that contain both a Wi-Fi and an Ethernet interface on them as a means for you to connect your libre computer to the 802.11ac 5 GHz network.
Note that 802.11ac is only specified for 5 GHz. 2.4 GHz is provided as a fallback on 802.11n. Also note, despite the fact that 5 GHz has a lot more bandwidth per-se, it is much more heavily regulated than 2.4 GHz in the interest of avoiding interference with radar devices. So it turns out that the usable bandwidth on 5 GHz is not as great as you would think on first thought.
20180829/DuckDuckGo 802.11ac libre 5 ghz
20180829/http://lifeinide.com/post/2017-05-08-linux-5ghz-wifi-with-no-drivers-problem/
20180829/https://www.smallnetbuilder.com/wireless/wireless-features/31694-why-80211ac-will-kill-the-5-ghz-wi-fi-band
20180829/https://en.wikipedia.org/wiki/IEEE_802.11ac
Multi-user MIMO is another nice feature that 802.11ac provides.
20180829/https://en.wikipedia.org/wiki/Multi-user_MIMO