LibreCAD is a 2D CAD program only. OpenSCAD has no sketching capability but can extrude an imported DXF profile. So both can be used together. OpenSCAD uses a simple scripting language to build models.
#FreeCAD is more feature complete and allow for the traditional GUI input with a mouse work flow. Starting a sketch and adding measurements as you go is exactly how its Sketcher works. FreeCAD is quite a beast, you need to be prepared to dedicate some time to master it.
FYI TinkerCAD is a web app, you need an Internet connection.
While it's free, it's not FLOSS. It's owned by Autodesk (of AutoCAD fame), a company not known for fair business practices... They once tried to copyright DWG.
I won't discourage people from using TinkerCAD, there's nothing as easy to use apparently. But do so in full knowledge that at anytime, Autodesk may change its terms of service, or even shut the service down. They've done it before, and will again.
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