Kubuntu, the KDE flavour of Ubuntu, seems to work very well out of the box when installed on a new machine, needing very little configuration. One instance where you need to take that extra step is to allow taps on a laptop touchpad to be interpreted as clicks. For some reason I can’t imagine, this is not enabled by default.
Note: I’m using Kubuntu 20.04 LTS with KDE Plasma 5.18.5.
To enable this, you need to go into System Settings -> Input Devices -> Touchpad. You can reach the Touchpad settings directly by searching for “touchpad” in the search box (top-left in System Settings).
Once in the Touchpad settings, all you need to do is enable the “Tap-to-click” option. Once this is enabled, there are additional settings you can customise, but there’s typically no need to change them.