KDE is that. The two things I don't like about it are: KIO integration with GTK apps even with kio-fuse installed, and not having dbus based configuration system like gsettings/dconf.
Not sure if it's a NixOS bug, but even other KDE apps have hit-or-miss KIO integration for me; e.g. Krusader cannot open my MTP devices, while Dolphin can.
