Shadow DOM styling from the outside

I did try many methods, including those described here. Since I’m using an external Web Component lib, I don’t have access to modify these components. So, the only solution that worked for me was using JS querySelector, like this:

document.querySelector("the-element.with-shadow-dom")
  .shadowRoot.querySelector(".some-selector").setAttribute("style", "color: black");

Not the best solution, not suitable for large stylings, but does work for little enhancements.

@John this was tested with Chrome 83.0.4103.116 (still going to test in Safari) and I did for Ionic (v5) ion-toast component. Here is the (almost) real code I used:

  import { toastController } from '@ionic/core';

  let toastOpts = {
    message: "Some message goes here.",
    cssClass: "toast-with-vertical-buttons",
    buttons: [
      {
        text: "Button 1",
        side: 'end'
      },
      {  
        text: "Button2",
        side: 'end'
      },
      {
        icon: "close",
        side: "start"
      }
    ]
  }
  toastController.create(toastOpts).then(async p => {
    let toast = await p.present(); // this renders ion-toast component and returns HTMLIonToastElement
    toast.shadowRoot.querySelector('div.toast-button-group-end').setAttribute("style", "flex-direction: column");
  });