Firefox is a web browser that has been a opensource favorite since its Netscape days. Now, after beating off Internet Explorer only to be over taken by Chrome, the speed difference between it and Chrome is minimal and with the blocking of many trackers in many ways Firefox is ahead of Chrome especially for privacy.
Firefox should already be installed on Kubuntu 20.04 but if for some reason it isn’t then it can be reinstalled by opening Konsole and typing,
sudo apt install firefox
After installation you can find it by searching in the main menu or under Menu/Applications/Internet.