1 Load default scene
2 Press Play and go to Scene tab
3 Choose camera and rotate it so the particle system gameobject is out of the frustum. The particle system no rendered if only the emitter isn't on screen, but particles should be on the screen.

Also look at the user's description.

1. Particles are culled when the particle system gameobject is out of the
frustum of the camera (be it scene or game camera)

2. In my example scene I attached, load the default scene. Run the project.
You'll notice a perlin noise texture is generated and a particle system is
made with particles. Now move the camera (scene) so the particle system
gameobject is out of the frustum.

3. Expected results: The particle system still gets rendered even though
the emitter isn't on screen. For example, a long line of particles being
produced from a rocket should still be on screen regardless of whether the
rocket is on screen.

4. Actual results: The particles generated get culled immediately when the
particle system gameobject is offscreen.