Currently, Dorico Pro 2 and Dorico Elements 2 run on versions of macOS back as far as Mac OS X 10.11 El Capitan.
Due to changes in the underlying Qt framework that Dorico relies upon, the next major version of Dorico, to be released later in 2019, will no longer run on MacOS X 10.11 El Capitan. It will require at least macOS 10.12 Sierra.
There are no expected changes to the minimum supported operating system on Windows, but we will provide further updates as needed.