Netpaln is default network configuration tool introduced in ubuntu 17.10 and if you want to disable this to go back to old ways of configuring network use the following procedure.
Netplan is a YAML network configuration abstraction for various backends (NetworkManager, networkd).
It is a utility for easily configuring networking on a system. It can be used by writing a YAML description of the required network interfaces with what they should be configured to do. From this description it will generate the required configuration for a chosen renderer tool.
Note:- This is not recommended and this is for advanced users only
Edit the /etc/default/grub file
sudo nano /etc/default/grub
Add the following line
Save and exit the file
Now update the grub using the following command
You need to install ifupdown package
sudo apt install ifupdown
Now you can add all the interface details in /etc/network/interfaces file and reboot the ubuntu PC/server.