This likely means that the library (@angular/material/snack-bar) which declares MatSnackBar has not been processed correctly by ngcc, code example

Example 1: This likely means that the library (@angular/material/radio) which declares MatRadioModule has not been processed correctly by ngcc

// package.json

{
  "scripts": {
    "postinstall": "ngcc"
  }
}

Example 2: This likely means that the library (@angular/material/radio) which declares MatRadioModule has not been processed correctly by ngcc

//Also try running the serve command again