How to style ng-bootstrap components in Angular 2

For angular version 8.3, ::ng-deep is recommended

::host .license-circle {
  width: 10px;
  ... other styles
}

:host ::ng-deep .tooltip {
  &.in {
    opacity: 1;
  }
}

One thing that we need to remember is that ::ng-deep, /deep/ & >>> have been deprecated in angular 9. So, finding some other long term solution would be a good thing to do at this point. Check out the docs for more.

As mentioned in the comment, the selectors should start with :host

:host .license-circle {
    width: 10px;
    ... other styles
}

:host /deep/ .tooltip {
    &.in {
        opacity: 1;
    }
}