bluetoothctl: 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:

/usr/bin/bluetoothctl - from package: bluez

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