netplan: command not found

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/sbin/netplan - from package: netplan

You may install the required package with command apt-get install {package}

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