For me, it turned out to be the rear thru-axle.
I had to tighten it really firmly to make the creaking go away.
I also had a direct mount hanger installed at the time, but I have since switched back to the original UDH derailleur hanger, and now it's fine.
Additionally, I swapped the included bottom bracket for a Praxis bottom bracket. It might be worth checking the rear axle torque before going crazy with the bottom bracket spacers!
appreciate this. creaks can be difficult.
when i developed one on my gravel bike, i thought it was my bottom bracket after ruling out the seat, seatpost, and pedals. the shop did too and replaced the bottom bracket, but it didn't solve it. they ultimately tracked it down to the rear derailleur hanger as being slightly loose or some dirt/dust had gotten in between the hanger and frame. they just cleaned it and tightened it up and i was all good.
so agree, cleaning stuff and making sure everything is tightened up to spec before throwing parts at it is a good (and much cheaper) idea.