in v8 core-js was removed as i saw, so can u remove it from package.json dependencies?
after migrate my project (big) maby will see something else
The only peer dependencies are "@angular/core": ">=7.0.0" and "rxjs": ">=6.3.0", core-js is only used for testing and building the library, but is not required to use it.
Since the version required for Angular is ">=7.0.0", it should work with v8 as well
currently the library is not working with angular 8. Is there any workarounds other than downgrading angular?
@paddyfink it is working with v8, see: https://stackblitz.com/edit/github-47bavg?file=package.json
@ocombe It "should" work with v8 but it does not work with ng update

Yes that's because of how semver works, >=7.0.0 will work with 9.0.0 but not 9.0.0-next.3, you can try it here: https://semver.npmjs.com/
None of the beta / next releases will be compatible with >= because it only takes stable releases
Most helpful comment
The only peer dependencies are "@angular/core": ">=7.0.0" and "rxjs": ">=6.3.0", core-js is only used for testing and building the library, but is not required to use it.
Since the version required for Angular is ">=7.0.0", it should work with v8 as well