Particles not colliding with GO that has rigidbody?

I would think this is a simple answer, but have not found one that works.

I am using the Enviro Weather system rain effect. They have a nice “splash” droplet that spawns when the raindrop hits something. Almost…

Long story short - I have the default cube with a box collider. The rain hits it and spawns the droplets.
If I put a rigidbody on the cube, the droplets stop.
I have:

Collision Quality set to High

Dynamic collisions enabled

Continuous dynamic collisions set on the RB

Tried kinematic on and off on the RB

I’ve tried pretty much every setting on both the RB and Particle->Collision section.

Why don’t the particles collide with the GO with a rigidbody?

Unity 2021.1.11f1

@SalokaB Have you tried assigning layers to your particles and cube and setting collisions through the layer collision matrix?