Capture One 20 (13.1.3) is the last version that supports Windows 7.
Of course, any versions of Capture One that claim to support Windows 7 will continue to do so.
As a result, we recommend updating your operating system if you would like to run the future versions of Capture One. However, you can also run the current version of Capture One on your Windows machine if that fits your workflow.
NOTE: Any bugs discovered on any version after Capture One 20 (13.1.3) when using Windows 7 will not be reported to R&D.