Currently, the only confirmed actor in the Garfield movie is Chris, but there are some big names who will be a part of the production. According to The Hollywood Reporter, the script is being written by David Reynolds, who worked on Finding Nemo, and the movie is being directed by Mark Dindal, who worked on Chicken Little. These two have worked together before on the 2000 Disney movie The Emperor’s New Groove.
Jim Davis will also be an executive producer on the film. But one major difference between this Garfield movie and previous ones is the voice of the main character himself. In the previous two movies, the cat was voiced by Bill Murray. It's unclear why he isn't returning to the role for this film.
You can watch both previous Garfield movies on Disney Plus.