Capped 38 times by Ireland, the New Zealand-born Carbery played for Leinster between 2016-18 before joining Munster.
He was back up to since-retired Jonathan Sexton at the 2019 Rugby World Cup in Japan.
Carbery will be up against France fly-half Matthieu Jalibert to nail down the starting number 10 spot.
Other signings confirmed by club president Laurent Marti include once-capped Springbok centre Rohan Janse van Rensburg from the Sharks and Oyonnax winger Enzo Reybier.