Project Chrono is described as 'Open-Source Multi-physics Simulation Engine in C++' and is an app in the Development category. There are three alternatives to Project Chrono for Windows, Linux and Mac. The best alternative is Matali Physics. It's not free, so if you're looking for a free alternative, you could try BepuPhysics or ReactPhysics3D.
BepuPhysics is a pure C# 3D real-time physics simulation library. The BepuPhysics and BepuUtilities libraries target .NET Standard 2.0 and should work on any supported platform. The demos are built on .NET Core 2.1 and require DX11.