Models @ MakeWithTech is on only search application and customizer for OpenSCAD models.
With the release of macOS Big Sur, the FreeCAD pre-releases for version .19 found on the Github release page are not currently working. This post provides a solution.
The DrVax YouTube channel features a playlist highlighting popular 3d design tools capable of creating models for 3d printing.
FreeCAD is an open-source parametric CAD application installable on Windows, macOS, or Linux. Watch the following video to begin your journey into CAD. Learning CAD, while not trivial, is worth the effort.