Comment by abe_m
We have OpenCASCADE, GCAL and Solvespace. The later two are missing quite a few features relative to OpenCASCADE. Then there is Parasolid, ACIS, and whatever they call the kernel in CATIA. There are a few around. But perhaps there aren't that many ideas for innovative features for people who are interested in the area to create something new.
The other "decent" commercial one that can be licensed is C3D (ASCON/АСКОН uses a CAD kernel based on it in КОМПАС 3D) but it is Russian and thus currently "behind sanctions".
Here is a bit on it from the author of Plasticity: https://www.youtube.com/watch?v=WvwiH1DOK1M it initially was based on C3D.