Its not often you see 'fillets and chamfers' are tip-line features in the readme for CAD packages. But good on you for building something.
Well the readme states the following:
Solvespace on the other hand gets the workflow part right, but falls short by not importing STEP and the geometry kernel not supporting chamfers and fillets.
So I assume that's where that comes from.
Roughly every other week there is a new "The (programmable) CAD that fixes everything!" post on the front page, just for me to open them up excitedly and noticing that they use a mesh kernel and will thus never be able to provide fillets and chamfers painlessly (for the user). All while they are absolutely essential for a lot of designs, especially in 3D-printing, a well-placed fillet/chamfer can make the difference between an object that breaks upon looking at it funny and one that can bear significant load.
https://github.com/WillAdams/gcodepreview
Needs a full-on re-write to make the G-code export (and import) work well, but lately I've been focused on exporting to DXFs w/ colour/layer tagging which was just added as an import feature in the CAD tool my side-gig employer does.
Source: been there, done that.