This version of CLI is only compatible with Angular versions 0.0.0 || ^10.0.0-beta || >=10.0.0 <11.0.0, but Angular version 9.1.3 was found instead.

JavaScript
npm uninstall -g @angular/cli
npm cache clean
npm install -g @angular/[email protected] install --save -dev @angular/cli@latestng update @angular/cli @angular/core --allow-dirty --force
Source

Also in JavaScript: