This repository demonstrates how to directly interact with Unity Physics without using Unity's Entity Component System (ECS)†.
2021-12-05.12-06-13.mp4
Unity Physics is a deterministic‡ and stateless physics engine by Unity Technologies. You can read more about it here. Although it comes packaged with prebuilt components for Unity's entity component system, the core engine is decoupled from ECS. Determinism and statelessness are very useful for networking, where consistency in physics between server and client is important.
† Unity Physics does depend on the Entity struct itself from ECS.
‡ Unity Physics is described as "deterministic", but I assume this is restricted to determinism across a single platform due to inconsistencies between some floating point arithmetic between platforms (e.g. ARM vs x86).