Hi all,
A little over a week ago, ocaml-windows.5.1.1 was added to ocaml-cross/opam-cross-windows 
The opam-cross-windows repository provides opam packages that build libraries and binaries targetting the windows platform from linux and macos hosts using the mingw-w64 cross-compiler and mxe.cc for extenal dependencies.
The addition of a ocaml cross-compiler version 5.1.1 makes it possible to compile code using the awesome new set of feature of the ocaml 5.x releases!
A lot of packages still need to be updated to support the ocaml 5 compiler. Fortunately, adding new dune-based packages has become remarkably easy thanks to dune’s great cross-compilation support. Also, the CI could use some love.
If you find it useful, feel free to come help!