FLRW, a lumpy loaf of raisin bread is finite and the dough expands and carrys the raisins { galaxies } with it as it expands.
Any finite phenomena has a geometric center related to its outer surface boundaries. Even if the boundaries are in dynamic change, lumpy or other-wise.
Any talk of infinite occupied space is ignorance of wholistic integrity, as infinite cannot have cannot be niether whole nor have systemic or structural integrity.
These people who want to go off into infinite Universe cannot even barely grasp our finite Universe. Just ignorance spouting out nonsense.
..........................Space( * ) i ( * )Space..............................
Take a concept of a square and find its 2D center, now fold square into a tube and find the 3D center. Now conceptually fold tube around to meet itself and locate the both prior make center points.
A balloon has a center 3D volume. Let air out of balloon and and place scissors into the opening and cut on trajectory to the approximate, diametric other end of the balloon and lay it out as if in a 2D area. It will have wrinkles and folds but all of that topology can be accounted for and we find exact center as related to the 2D area of the
laid out balloon.
Our sun Sol, has a degree of sphericity, yet a changing center point can be assigned to its minute changing outer geometric surface distance over at least three seperate meaurements, tho the more the merrier for refinning accuracy.