I had no idea kio-fuse was being worked on. This is awesome! gvfs (and its FUSE implementation) was my favorite feature of GNOME and was the reason I primarily used Nautilus on KDE on my work VM.
Took a while but it does work, bar a few minor issues. I have problems with certain applications not understanding Dolphin has already authenticated to a share. For example VLC will only open a file if the URI to the share contains the user name required to authenticate (smb://user@fileserver/Video).
[0]: https://bugs.kde.org/enter_bug.cgi?product=kiofuse&component...