aptitude install linux-headers-amd64
aptitude install linux-source-amd64
tar xf linux-source-4.19.tar.xz
cp ../linux-headers-4.19.0-4-amd64/Module.symvers .
make oldconfig # aptitude install libelf-dev
vim .config # check CONFIG_ATH9K=k
make prepare # aptitude install libssl-dev
make modules_prepare
make SUBDIRS=scripts/mod
make SUBDIRS=drivers/net/wireless/ath/ath9k modules
cp drivers/net/wireless/ath/ath9k/ath9k_htc.ko /lib/modules/4.19.0-4-amd64/kernel/drivers/net/wireless/ath9k
depmod
modprobe ath9k_htc