I've played around with most of the solutions in this space (OnShape, Fusion360, FreeCAD, Solvespace), but honestly at this point would probably just end up paying for the Solidworks hobbyist license; it's like $4/month and I have a Windows desktop available. That said, there's been some consensus built over the past few years about what the next-gen CAD software should probably look like, ranging from modern scripting capabilities to version control and intermediate shape representations.

A big of the attraction of re-building this kind of foundational software isn't the base capability (commercial 3D CAD has barely even seen incremental improvements for more than a decade, in large part because it's just pretty well solved in the existing programs), but that a modern kernel would be a major step forward for unblocking implementation of some of those other capabilities.