I was able to successfully build spice-webdavd from package.yml today, but I still need to figure out how to correctly install the service. Supposedly once this is installed and the daemon is running, GNOME Boxes should have an option to set up a shared folder between guest and host. If I get some time later on, I will pick this up again and if it works well, I can put in a package request. It would be nice to get this working out of the box!
