Unable to locate package unetbootin code example

Example: E: Unable to locate package software-properties-common 2020

# that can be due to offline installation of the distro

# open the sources.list file using the following command
sudo nano /etc/apt/sources.list

# check if the file contains the following lines
deb http://http.kali.org/kali kali-rolling main non-free contrib 
deb-src http://http.kali.org/kali kali-rolling main non-free contrib

# if it doesn't have these 2 lines, just add 'em at the beginning of the file and 
# press ctrl+o save changes then ctrl+x to exit

# don't forget to type the following command in the terminal after you finish
sudo apt update