Switch to open-ath9k-htc-firmware
Ben Hutchings, the maintainer of Linux & firmware in Debian, wrote:
the
ath9k_htc
firmware in firmware-nonfree has been replaced by free firmware built from open-ath9k-htc-firmware
aka. https://tracker.debian.org/pkg/open-ath9k-htc-firmware
So we should install firmware-ath9k-htc
and ensure we install a version of firmware-atheros
that's new enough to be compatible.