  The Fabbri-Russo model is a generalized model of a two-dimensional dilaton
gravity theory with various parameters "$n$" describing various specific
gravities. Particularly, the Russo-Susskind-Thorlacius gravity model fits the
case $n=1$. In the Fabbri-Russo model, we investigate Page curves and the
entanglement island. Islands are considered in eternal and evaporating black
holes. Surprisingly, in any black hole, the emergence of islands causes the
rise of the entanglement entropy of the radiation to decelerate after the Page
time, satisfying the principle of unitarity. For eternal black holes, the
fine-grained entropy reaches a saturation value that is twice the
Bekenstein-Hawking entropy. For evaporating black holes, the fine-grained
entropy finally reaches zero. The parameter "$n$" significantly impacts the
Page curve at extremely early times. However, at late times and large distance
limit, the impact of the parameter "$n$" is a subleading term and is
exponentially suppressed. As a result, the shape of Page curves is
"$n$"-independent in the leading order. Furthermore, we discuss the
relationship between islands and firewalls. We show that the island is a better
candidate than firewalls for encountering the quantum entanglement-monogamy
problem. Finally, we briefly review the gravity/ensemble duality as a potential
resolution to the state conundrum resulting from the island formula.
