With this Lightroom Classic 10.0 release Adobe has dropped support for Windows 7 and for Mac OS High Sierra (10.13).
You will only be able to install LrC 10.0 with one of the following operating systems:
- Windows 10 version 1903 and later
- Windows Server 2016 and later (Windows 10 version 1809 is not blocked, to support Windows Server 2019)
- Mac OS Mojave (10.14) and Catalina (10.15)
Adobe is also preparing to support Mac OS Big Sur when it is released later this year, and to provide a native version of Lightroom Classic for Apple Silicon.