While not as capable and well supported as Fusion, the two top alternatives that I am aware of are: https://www.openscad.org/ and https://www.freecadweb.org/
With FreeCAD being closer to Fusion than OpenSCAD.
With FreeCAD being closer to Fusion than OpenSCAD.
The scripting makes making technical parts often much easier, and more maintainable. I for instance wanted to replace a metal rod in an antenna with a smaller diameter, and changing several mounting parts for the rods became changing a single variable. Plus, being eble to comment scad files makes it much easier to meaningful share parts (the STL files on Thingiverse are hard to modify).
The usual caveats apply: people tend to either shy away from the few days it takes to learn OpenScad, or, once they invest the time, there's a tendency to over-engineer scripts and not focus on tasks at hand ;)_
One big caveat, which I've experienced on several past versions is that it freezes up completely (like freeze freeze) for 3 - 15 seconds whenever you open it, saves files etc.
I have a 2017 MacBook Pro 16 GB, with MacOS 10.14, so I don't think it should be any problems, but.
I'm just attributing it to "these are quirks you accept when going full open source and not paying for it"
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