https://bugs.winehq.org/show_bug.cgi?id=47955
--- Comment #8 from Ben R divestoclimb@gmail.com --- I don't think Vmindefault is intended to be run standalone, it's usually launched from Vminteq17. Once Vminteq17 has run it will copy a bunch of files into the chosen user folder location. So Vmindefault can be tested in isolation, but you'd need the user folder to be created and populated first, which I have in my environment since I was able to get that part working with dotnet45.
What's odd is that when I run Vmindefault I get a System.IO.DirectoryNotFoundException: Could not find a part of the path "Z:\home\benr\benr\userfolder.txt". My $HOME is /home/benr so I don't know where the extra "benr" is coming from. I got curious to see what would happen if I made that path valid with a symlink, and I instead got System.ArgumentException: Illegal characters in path.
That pull request looks promising. I'll try building a patched Mono and see what happens.