Not sure what it'll be then. Assuming it is/was a real working fireplace there will be a recess of some kind, but like you say you might just have to smash it out and see! Be sure to post pictures of course...
My two 2p are; 1. Look all around for screws or possibly filled in screws that hold the fire place on. I think ours had about 6 screws holding it on to batton which were fixed to the wall. Obvs Ymmv.
It’s a new enough build, mid 90’s, but I guess it’s hard to tell short of just pulling it out and assessing the situation.