Might I ask, why exactly do you feel the need to have a webapp for CAD rather than a hard client?
Freecad in a VM with a remote viewer like guacamole?
Ideally you could use moonlight but that is not web based
What about solvespace web build: https://github.com/solvespace/solvespace/tree/emscripten#building-for-web
Check out Kasm too, you can easily install blender into it.
Would love to learn if it exists too. I use it often.
The only other way I know how to CAD is https://github.com/pythonscad/pythonscad
Unrelated but BTW FreeCAD is fully python scriptable. In fact, as I understand it, every operation is first translated to python code.
Yeah, and it outright isn’t documented.
FreeCAD’s Python functions are all well organized in different modules. Some of them are already loaded (imported) when you start FreeCAD. Just try:
dir()
https://wiki.freecad.org/Python_scripting_tutorial
https://wiki.freecad.org/FreeCAD_Scripting_Basics
https://wiki.freecad.org/Python_console
https://wiki.freecad.org/Power_users_hub
https://wiki.freecad.org/Debugging#Python_Debugging
https://wiki.freecad.org/Profiling
…
There is also Cascade Studio (Demo). Sadly development has stalled, it was a really cool project.
Probably not at all what OP is looking for though since TinkerCAD is just sketch/primitive type workflow, not like openscad.