If you fly near a Body you can land on, disengage into normal space (still well beyond Orbital Cruise) and have i.e. Signal Source Objects, any dropped Canisters or set the own Ship to FA OFF - you'll see it all getting pulled towards the Planet as you'd expect.
For the longest time, the Script that attempted to simulate Gravity even had (might still have, unsure) differences between different classes of Objects - causing i.e. Cargo Canisters to accelerate at a different speed than debris and yet different to your own Ship. Notably, fixed assets like an abandoned Ship... remained stationary - leading to some awkward moments.
But if you do the same near a Black Hole, any Star, any Gas Giant or a Planet with Atmosphere - nothing happens. Zero Gravity, no matter how close you get (upto the Body Exclusion zone of very high Gravity Bodies).
The reason for that appears to be that those simply have no gravitational effects scripted, hence nothing in their proximity accelerates towards them as expected.
So for example dumping that Canister of Biowaste into a Neutron Star or Black Hole? Doesn't work, nothing moves. No Gravity.