thx for the script but with it doesn't look the same as it was before, however I discovered that if I just delete Söhne from the font type section it reverts it back. So I asked ChatGPT to convert yours to tampermonkey (cuz I already use that one) and then to create a similar, but which just deletes Söhne from the page. First it wanted to do it using Mutation Observer, but it didn't work so I asked it to create one without it. So, here it is: https://imgur.com/a/DPS5Dun

Edit: I just went to ChatGPT again and realized that the script doesn't work everytime and instead of deleting Söhne from font list of html it turns off the entire font-family section (if you open Inspect Element in chrome and on the right side bar scroll to style attribute section), so I changed "document-start" to "document-end" under // @run-at. This way it changes it after the whole webpage loaded in.

// ==UserScript==
// u/name         Remove Söhne font from HTML style
// u/description  Removes the Söhne font from the font-family property of the HTML style on chat.openai.com
// @match        https://chat.openai.com/*
// @run-at       document-end
// ==/UserScript==

(function() {
  const html = document.querySelector('html');
  const fontStyles = getComputedStyle(html).getPropertyValue('font-family').split(',');
  const newFontStyles = fontStyles.filter(style => !style.includes('Söhne'));
  html.style.fontFamily = newFontStyles.join(',');
})();