2020 240d hse dynamic, loud rumble vibration.

This may help others and has been discussed with a video of the noise on other forums.
The noise occurs randomly and makes the car sound like an old diesel tractor when it’s just started up. It’s random and the car can’t be forced to make the noise.
It turns out the fix is to either realign the whole exhaust system or replace it.
Seems to be a resonance of the baffles, or a poorly constructed exhaust element that causes the problem.
Mines ok now.
Dave Twatter