  A Page curve for an evaporating black hole in asymptotically flat spacetime
is computed by adapting the Quantum Ryu-Takayanagi (QRT) proposal to an
analytically solvable semi-classical two-dimensional dilaton gravity theory.
The Page time is found to be one third of the black hole lifetime, at leading
order in semi-classical corrections. A Page curve is also obtained for a
semi-classical eternal black hole, where energy loss due to Hawking evaporation
is balanced by an incoming energy flux.
