Ubuntu how to check if package is installed

dpkg -l | grep dhcp

The above command will help to search for package that has name hdcp 

result will be something like below 

ii  isc-dhcp-client                            4.4.1-2.1ubuntu5.20.04.3            amd64        DHCP client for automatically obtaining an IP address

ii  isc-dhcp-common                            4.4.1-2.1ubuntu5.20.04.3            amd64        common manpages relevant to all of the isc-dhcp packages

Now to list all packages below can be used

dpkg -l | less 

references:

https://askubuntu.com/questions/423355/how-do-i-check-if-a-package-is-installed-on-my-server