I don't usually post specific train changes, but I think this is an important information for many travelers here.
Thello (https://www.thello.com/Marseille-Milan/Horaires/index.html) just started selling tickets for its new train service Milan-Marseille via Genova, Monaco, Nice and Cannes.
The service is not as fast as I'd like, but it sill offers a convenient way for certain typical itineraries (like combining Cote d'Azure with Cinque Terre) that often get mentioned here.
There is just one daily train per direction
Marseille (15:30) => Milano (22:50)
Milano (15:10) => Marseille (22:29)
... but the times are convenient, especially for shorter trips like Milano-Nice.