Customize the dashboard / welcome page

yes you can! In admin/app.ts at the bootstrap function, you can add some javascript to add css to the page and override te content. But I prefer @dgrebb solution.
here is a sample

bootstrap(app: any) {
      const styleTag = document.createElement("style");
      styleTag.innerText = `
      a[href*="/dashboard/plugins/cloud"], a[href*="/strapi/strapi/releases/tag/v"], a[href*="strapi.io/"], a[href*="cloud.strapi.io"] {
        display: none;
      }
      nav[aria-label="Settings"] ol li:nth-child(2), nav[aria-label="Settings"] ol ol li:nth-child(3) {
        display: none;
      }
      aside[aria-labelledby="join-the-community"], .home-page #main-content>div:first-child>img {
        display: none;
      }
    `;
      document.head.appendChild(styleTag);
      const isHomePage =
        window.location.pathname === "/dashboard" ||
        window.location.pathname === "/dashboard/";
      document.documentElement.classList.add(
        isHomePage ? "home-page" : "not-home-page"
    //   );
  },

This will hide everything in the content of dashboard/ page an somethings at settings
Then now simple add some tags via javascript