Not tried different pedals, but I’ve tried the crank and BB on a different frame and silence, so I don’t think it’s them. Good shout on the QR, I’ll double check that but I’ve tried it with two different skewers and it’s the same, so probably not.
It’s a (brand new!) XT HTII BB, with FSA Gravity cranks. They’re pretty old, but since it doesn’t do it on the other frame I think I can rule out the cranks. Pretty sure it’s not the headset, with the bike in a workstand if I pull the back brake I can rock the cranks and make it creak. I didn’t actually stand on the cranks with it upside down (though that would have been amusing!) – actually stood on the rear brake lever and put pressure on the pedal with my hands.
Had a good look at the frame and can’t see any cracks!
And it’s a Lyrik.