TBH I don't like FreeCAD - I fell like it's like recommending Gimp as a serious alternative to Photoshop. With enough effort and deep knowledge you can almost achieve similar results but you have to invest multiple times as much time. The saving in licencing cost is very quickly eastern up by the increased labour cost.
There is an alternative that has come a long way IMHO, though: BlenderBIM. They are still not quite as good as ArchiCAD and such but it runs natively on Linux and is very neat so far.