Yes it is that simple if you are on one of the supported hardware devices. If you aren’t on one of those devices, you will have to install the OS and supervised homeassistant yourself. Which isn’t really that hard, but harder than just dumping the image to disk and booting from it.
Other option is installing in a VM of course. Then you don’t need to worry about the OS of the host. But you will lose some performance and have a tougher time with some hardware devices (people have really been struggling to get Google Coral and HGI80 working in VM).