I encountered following the error whilst updating from angular 8 to 9 and running
ng update @angular/material:
Package "@angular/flex-layout" has an incompatible peer dependency to "@angular/cdk" (requires "^8.0.0-rc.0", would install "9.0.0").
Fixed by:
npm uninstall @angular/flex-layout
ng update @angular/material
npm install @angular/flex-layout
You have to update both dependencies at the same time. Had the same issue when only updating one at a time.
ng update @angular/material @angular/flex-layout
Hope this helps.