Windows 7/ 8/ 10. 2GB of RAM. Graphics drivers: OpenGL 2.1 or higher is required.
There are no minimum CPU requirements on top of that required to run Windows.
Everything from Mavericks (OS X 10.9) and newer.
We perform testing on Ubuntu based distributions but Hiri works on other distros too. We have users who are successfully using it on Fedora, OpenSUSE, Arch...
There is an ongoing effort to package and distribute Hiri as a snap for easier installation.