  We compute the subregion entanglement entropy for a doubly holographic black
string model. This system consists of a non-gravitating bath and a gravitating
brane, where we incorporate dynamic gravity by adding a DGP term. This opens up
a new parameter directly extending previous work and raises an important
question about unitarity. In this note we analyse which theories in this big
parameter space, will have unitary entropy evolution, in particular, we will
distinguish which of those will follow a Page curve.
