Unmet dependencies issue in ubuntu 20.04

It looks like you have trusty repos added to your system. These will need to be removed because adding sources from other Ubuntu versions can break package management and can prevent you from updating or adding new software.

Make a backup of /etc/apt/sources.list and then edit that file removing the lines that have trusty. You can also "comment out" individual lines by adding a # in front of them. Commented lines will be ignored in your sources lists.

If you don't see any trusty lines in /etc/apt/sources.list, they could be in another .list file under /etc/apt/.

Alternatively, you can review and disable sources in the GUI software center.

After you do this, you should run sudo apt update and then try again with the sudo apt --fix-broken install and then sudo apt upgrade. If this resolves errors and brings your system up-to-date you should be able to install new software.