opam-repository-mingw does need Cygwin for development, but the resulting binaries won't depend on it. I was able to port a CLI application with a lot of dependencies without much trouble.

Alternatively, Esy supports Windows and might provide you with a smoother experience. Esy is an alternative to opam cli tool that feels more like npm and supports OCaml projects and opam packages.

https://fdopen.github.io/opam-repository-mingw/

https://esy.sh/en/

https://github.com/esy-ocaml/hello-ocaml