The latest versions of Omnisphere 2, Keyscape, Trilian and Stylus RMX are natively supported on both M1 and Intel Mac computers, on the following operating systems: MacOS 11 Big Sur, MacOS 10.15 Catalina, and MacOS 10.14 Mojave. Beta versions of macOS are not supported.
Regarding Omnisphere 1, which was released in 2008 and was publicly available through April 2015 (prior to the relase of Omnisphere 2) - Omnisphere 1 is officially supported on MacOS 10.6 Snow Leopard through MacOS 10.10 Yosemite; it will not install on 10.12 Sierra and later. Older versions of our instruments are supported on the operating systems that they were designed and advertised to run on.
If you would like to use an older version of Omnisphere, make sure it is installed on a supported operating system. We recommend upgrading to the latest version of Omnisphere here, which contains many added features and sounds in addition to compatibility with the latest operating systems and full backwards compatibility with older versions of Omnisphere.