I'm trying merlin 3.4.2 with dune 2.8.2 under native Windows (msvc) on Cygwin (no opam). When launching merlin the first time (ie the server is not running) under emacs the whole process hangs waiting for the spawned dune process to finish. If I open a follow-up session then merlin seems to work as expected. If I stop the server, the hanging behaviour comes back.

Glad to provide more details if it helps debugging.