Integrating the new physics engine is going well. I wrote a component that converts old-style colliders and rigid-bodies into the new style.
Sorry about the weird colors here. Unity today decided that I last renewed my license tomorrow (yup), and so right now, it thinks I'm unlicensed and gave me the light editor theme. The blue tint on the righthand-side lets me know when I'm in play mode, which is super helpful. It looks a lot less baby-blue when used with the dark theme :P
I'll pretty the UI up in time. For now, seeing everything is helpful.
It took me a while to work out where to get some mass related values right, so the dice rolled strangely, but now it's a little better.
Behind the scenes, a lot is going on, not least of which is that the physics is running with a fixed-timestep. This shouldn't be a big deal as a fixed-timestep is mandatory for stable physics across framerates. However, this is not *fully* supported in Unity's ECS, so I was concerned that it would be difficult.
Luckily for us, it was not. The physics engine is pretty great at giving you control, so I loop running the simulation for the required number of steps. If you have read about fixed-timestep before you'll know that you need to interpolate the results as the final step. The physics engine doesn't have that support for that out of the box, so we added a job to collect that information and apply it as we write the transforms back to the GameObjects.
With that done, I need to replicate the parts of the old physics API that we use. If I can get dice rolls working again then I should have replaced most of what we need.
Have a good one folks,
 yup I do know about the latest version making the dark theme free, but upgrading is risky and we are on a tight schedule right now.
 The interpolation is not hard, but the Unity folks have a lot more to support that we do, so we get to only handle the simpler case.
 The best known fixed-timestep explanation can be found over here. It's a good one.