is there anything similar to F-Droid for windows?
Do you mean a repository that builds the binaries from source, only distributes FOSS applications and reviews each of them? No, there’s not.
If you mean simply a package manager and installer, yes, there’s Chocolatey.
Of course, you could just run F-Droid on Windows.…
The Portable Apps client can be configured to install only opensource programs.
What is “The Portable Apps Client”?