Where did you get info for Angular 18?
We deprecated legacy components in v15 to be removed in v17. Even though they’ll not be part of the Angular Material v17 package, you can still update your apps to Angular v17 and use the v16 Angular Material package. This will be an option until v18, after which Angular Material v16 will no longer be compatible with newer versions of Angular.
[1] https://blog.angular.io/introducing-angular-v17-4d7033312e4b