It's hard to pin-point the sound on a youtube video but at 138K, it could be a worn cam chain if it's never been replaced.
I would buy a cheap stethoscope from Amazon and probe the chain cover with it, which will confirm it.
Another common noise is dual mass flywheel rattle, but again, it's difficult to isolate that on a video with all the other noises going on.
But at a basic level, if the engine sounds like a diesel inside the car (windows up, climate off) it's the chain. If there's a deeper rumbling/chuntering/clattering noise at feet level (passenger side), that's the DMF.