The Linux kernels available from Trisquel's repositories all free/libre. I
assume you are referring to the latest Linux-libre kernels (version 3.15.x),
like those in jxself's repository (see
https://trisquel.info/en/wiki/update-linux-libre-kernel for the different
options).
The TL-WN722N Wifi adapter has a AR9271 chipset. ath9k_htc drives it.
According to Chris, there is a bug with ath9k_htc on Linux 3.15.x (when
connecting to encrypted access points):
https://trisquel.info/en/forum/penguin-wireless-n-adapters-ath9khtc-bug-atheros-ar9271
Here is the bug: https://bugzilla.kernel.org/show_bug.cgi?id=78581
And here is a temporary fix:
https://www.thinkpenguin.com/gnu-linux/penguin-wireless-n-usb-adapter-gnu-linux-tpe-n150usb-tpe-n150usbl-tpe-nusbdb
