Make the GitHub web interface usable by turning off all its forced keyboard shortcuts that are interfering with browser and OS shortcuts.

gh_disable_shortcuts.user.js

// ==UserScript==
// @name           Disable all GitHub shortcut keys
// @description    Make the GitHub web interface usable by turning off all its forced keyboard shortcuts that are interfering with browser and OS shortcuts.
// @version        0.3.0
// @namespace      githubPls
// @include        https://github.com/*
// @updateURL      https://gist.githubusercontent.com/Rainyan/bdc81d2280936e26ac8690e7ac1292f9/raw/
// ==/UserScript==

const ALLOWED_KEYS = [
  'Backspace',  // allow removing lines in web editor
  'Tab',        // allow indenting in web editor
];

document.addEventListener('keydown', function(e) {
  if (ALLOWED_KEYS.includes(e.key)) {
    return;
  }
  e.stopPropagation();
}, true);