wlanctl-ng: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/sbin/wlanctl-ng - from package: linux-wlan-ng

You may install the required package with command apt-get install {package}
Error in other languages:
wlanctl-ng: bevel nie gevind nie
wlanctl-ng: comandă negăsită
wlanctl-ng: comando não encontrado
wlanctl-ng: commande introuvable
wlanctl-ng: command not found
wlanctl-ng: käsku ei ole
wlanctl-ng: không tìm thấy lệnh
wlanctl-ng: komanda nerasta
wlanctl-ng: Kommando nicht gefunden.
wlanctl-ng: kommandot finns inte
wlanctl-ng: komut yok
wlanctl-ng: nie znaleziono polecenia
wlanctl-ng: níor aimsíodh an t-ordú
wlanctl-ng: no se encontró la orden
wlanctl-ng: no s'ha trobat l'ordre
wlanctl-ng: opdracht niet gevonden
wlanctl-ng: parancs nem található
wlanctl-ng: perintah tidak ditemukan
wlanctl-ng: príkaz nenájdený
wlanctl-ng: příkaz nenalezen
wlanctl-ng: команда не найдена
wlanctl-ng: командата не е открита
wlanctl-ng: 命令找不到
wlanctl-ng: コマンドが見つかりません