Dia and gimp are ok, but they’re still quite behind the curve. I love floss and wouldn’t use the closed alternatives, but we got to know where we stand.
The ones I've seen in the wild are pvcs and ccc/harvest, but there are others. I think they usually try to brand it as part of a larger end-to-end SDLC tool or change management, or it's built to work with a specific proprietary system like Autodesk vault.
Blender had a reeeeaaally long way though, I remember a time where Blender was quite big already but Maya just was miles ahead in terms of usability. Nowadays they are not only even, Blender is probably used more often since it's not only free but more people know how to use it than Maya
I tried blender in those old days but stuck with cinema 4D at the time, blender really sucked. These days it's totally awesome kinda wish I had more time for it but I'm focused on other things.