Junction box under stairs?

Per NEC, is it acceptable to install a junction box on the underside of a staircase? This area is accessible by a small “gnome” door and gives access to the water heater, etc. My plan was to run 12/2 romex from a nearby receptacle (which faces into a living room on other side of drywall) and install junction box + doorbell transformer on the stairs. From there, the doorbell wire would make its way to the front door.

I’m mostly asking because I wasn’t sure if the movement of the stairs creates any issue. (There isn’t, but wasn’t sure over time.) There is a nearby stud I could put it on but it would have to go in front of/around insulation, since this gnome area is adjacent to exposed brick exterior wall.

Thanks for any suggestions.