Thanks for you help, Mörgæs. Anyway I formatted the USB and installed Kubuntu this time and it is running great so far. Actually it is taking much less memory (0.8 GB) than installing Ubuntu and then installing the KDE Plasma interface (1.2 GB). However, I could not find Chrome, Visual Studio Code and Thunderbird easily in Kubuntu's Discover but I managed to install them.

I just wanted to add this note to the thread in case anyone else had the same problem.