Installing via opam and using the cygwin method is supported and should be working fine (cygwin is just used for build - binaries still just link with mingw).

Installing via opam and using the cygwin method is supported and should be working fine (cygwin is just used for build - binaries still just link with mingw). That specific combination (ocaml + mingw) has a known problem with ocamlfind that's still awaiting a new release (see https://github.com/ocaml/ocamlfind/pull/112 https://github.com/ocaml/ocamlfind/pull/112). ocamlfind underpins quite a bit of the package ecosystem, so this one is annoying, as the mingw workflow is otherwise quite good.