Linux basic systems and a summary of the installation descriptions for their related accessories.
The basic systems are also known as minimal server installations they only have a recent Linux installation in console mode, without a graphical interface, and I add some basic extra packages (e.g. dwarf, openssh-server, etc.).
These can be considered as the foundation stones for further tutorials, as much of the tutorials will be based on these basic systems.
I install the basic systems in Virtualbox and put the finished virtual machine image file into the appropriate categories for the downloads. So anyone can download and try them on virtual machines. Or, if you just don't want to spend time with the installation, but also want to try the tutorials based on these, this is a more convenient solution for quick testing.
Installing the basic systems is not a prerequisite for using VirtualBox, so anyone can install it properly on their computer, I only install them on a virtual machine for portability so that I can share it here.
As time goes by, I try to make minimal installs with multiple distributions and multiple versions of them each so they can be more widely used.