These types of apps became fairly irrelevant with the advent of Web Fonts and sites that already do all of this.
There's Fontbase, Gnome's Font Manager, KDE's Font Viewer and FontForge that are still maintained.
The fact that you're asking for whatever tool to not use something like QT or GTK is asking for the moon here. These types of applications you describe are generally packaged with a DE for this very use. I don't think there's a real use-case for someone to develop this independent of any DE, honestly. That's what they're most useful for.

