Oh, I have some good news. I just couldn't believe that Ubuntu 20 is so badly broken that it is impossible to compile anything (surely, it would be noticed by someone!) so I installed it in a VM inside the VirtualBox and "build-essential" was installable without any problems (and gcc compiles programs just fine).
Now, the only difference between this install and the one I did in the morning on the physical SSD is that in the morning I ticked the option "Download upgrades while installing" (or left it checked). In the VM I unchecked this box. And also, in the fresh install in the VM I installed "build-essentials" WITHOUT doing "sudo apt update ; sudo apt upgrade". So, my guess is that one or both of these two things cause build- essential breakage: 1. Ticking "Download upgrades during installation" option during install. 2. Doing "sudo apt update ; sudo apt upgrade" BEFORE "sudo apt install build-essential" -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1920753 Title: Cannot install build-essential on fresh Ubuntu 20.04.2 installation To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/build-essential/+bug/1920753/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
