Incompatible peer dependencies found – upgrading Angular from 8 to 9

Looks like you glanced over one of the errors:

Package "@ngtools/webpack" has an incompatible peer dependency to "typescript" (requires ">=3.4 < 3.6", would install "3.7.5").

Try a lower version of @ngtools/webpack that works with TypeScript 3.4 to 3.5.

Alternatively, update your TypeScript version in the package.json to 3.7.5 and run npm update, then you should be able to update @angular/core & @angular/cli.