I've used a free 2D Draftsight in the past as an alternative to Autocad and had always been able to find an Ubuntu version to install. It looks as thought you can possibly get DraftSight 2018 SP3 free Beta for Ubuntu if that will serve your purposes, from here:
https://www.3ds.com/products-services/draftsight-cad-software/latest-version/
I think it is saying you can pay for extra tools and presumably it will be a RC rather than the beta version.
Also if you are interested in 3DCAD there is open source software, which again I haven't used for a while, called FreeCAD but used to be surprisingly good and well supported.
Now if anyone associated with Ubuntu Mate could create a snap for these.......