Why not write a very small script to give yourself what you want? This is the web after all, it is yours to manipulate & work as you wish! This is what makes the web different, better!

Here's a sample UserScript I scratched together in 3 minutes: https://gist.github.com/rektide/6d0af312d03482a7f3593f8fee7e...

  // ==UserScript==
  // @name        Url Filterer
  // @namespace   Violentmonkey Scripts
  // @match       https://news.ycombinator.com/\*
  // @grant       none
  // @version     1.0
  // @author      -
  // @description 6/30/2021, 5:27:00 PM
  // ==/UserScript==
  const BANNED = [
    "medium.com",
    "bariweiss.substack.com",
    "yoyodyne.example.net",
    "klein"
  ]
  
  // see if a link element includes the banned text
  function isBanned(link) {
    for (let ban of BANNED) {
      if (link.textContent.includes(ban)) {
        return true
      }
    }
  }

  // remove the 3 rows that make up a HN link
  function drop(link) {
    const row = link.parentNode.parentNode.parentNode.parentNode;
    row.nextElementSibling.remove();
    row.nextElementSibling.remove();
    row.remove();
  }
  
  // find all links, filter to only banned ones, then drop them
  [...document.querySelectorAll("span.sitestr")]
    .filter(isBanned)
    .forEach(drop)

Alas of course Google is actively killing userscripting extensions & lots of other really neat extensions, in a new security crackdown & desperate grasp for control & certainty. Lame. This tiny little script will need to become a fancy extension unto itself with a lot of boiler plate & crap, need a build processs. But for now!