This version of CLI is only compatible with Angular versions 0.0.0 || ^10.0.0-beta || >=10.0.0 <11.0.0, [ng] but Angular version 9.1.12 was found instead. code example

Example: This version of CLI is only compatible with Angular versions ^9.0.0-beta || >=9.0.0 <10.0.0, but Angular version 8.1.3 was found instead.

ng update @angular/cli @angular/core --allow-dirty --force