rxjs 6 Property 'of' does not exist on type 'typeof Observable'

You can now just import of from rxjs. So....

import { Observable, of } from 'rxjs';

// trivial example of what im trying to replace
  isLoggedIn(): Observable<boolean> {
    return of(true);
  }

If you are using Angular 6 /7 or 9

import { of } from 'rxjs';

And then instead of calling

Observable.of(res);

just use

of(res);