Installation of ser2net using the below command.
sudo apt update
sudo apt upgrade -y
sudo apt install ser2net -y
dmesg | grep tty
You should able to see filtered dmesg to check if your USB-Serial dongle had been recognised or not. If the dongle is multiple serial output them you should have multiple /dev/ttyUSB0…1,2,3,etc. See below image from my raspberry pi.