Well you can try monitoring Windows network connections, but Microsoft do seem to love obfuscating it with connections to multiple different domains that they own.

You can't even look at the Windows source code, so your question about reproducible builds seems to be moving the goalposts somewhat.

Also, is there something like "strace" on Windows?

Edit: just looked it up and Ubuntu doesn't enforce reproducible builds, although with their new "Monthly Snapshots", Canonical is moving towards reproducible build pipelines.