There is a certain amount of truth in the claim that Linux is not an operating system, but a series of operating systems all using the Linux kernel. That is clear in the case of the Android operating system, but it is less clear (and in the 1990s highly controversial) to call a Linux distribution an operating system. It is unclear if it is valid to call Ubuntu Linux an operating system, although I believe Ubuntu was the distribution that caused the controversy by being the first to call itself an operating system. It is difficult to maintain that Ubuntu is an operating system as it is possible to install Ubuntu then remove almost everything it installs except the Linux kernel and create your own bare bones version of Linux. It is often said that Linux is not an operating system because it just provides a way for other software to interact with hardware and it is the other software that makes up the operating system. The problem for such claims is that neither Windows nor MacOS would constitute an operating system on those grounds. The only candidates for being such an operating system would be those systems that refuse to release the necessary code to allow external programmers to produce software for their system. Much better to accept the more widely accepted notion that Linux is a operating system based around a Unix-like philosophy. That philosophy can be reduced to the notion that an operating system should be minimalist and modular. So whereas Windows removed the ability for alternative window managers to be used with their system by stopping Windows being based on MS-DOS, Linux continued to be a kernel that allowed a vast variety of tools to be built on top of it. Some of those tools are very large, such as the X Windows system that provides the graphical environment, and others are very small tools that can play very large roles in how Linux can be used. For example, in relation to RSI sufferers one of the most important small tools is Simple X Hotkey Daemon or sxhkd as it is normally known.