GreaseMonkey script for enabling shortcuts modifiers (eg. ALT + R for Fast Reblog) on Linux platform.

Modifiers_for_Linux.user.js

// ==UserScript==
// @name        Tumblr Shortcut Modifiers for Linux
// @namespace   mtrovo
// @include     http://www.tumblr.com/*
// @grant       GM_log
// @version     1
// ==/UserScript==

var KeyCommandsForLinux = (function ($) {
  return unsafeWindow.Backbone.View.extend({
    el: 'body',
    suspended: false,
    events: {
      'keydown': 'keydown',
      'keyup': 'keyup'
    },
    'keydown': function (e) {
      if (navigator.platform.startsWith("Linux")) {
        var code = e.charCode ? e.charCode : e.keyCode,
          modified = (e.shiftKey || e.ctrlKey || e.altKey || e.metaKey),
          i;
        var ctx = unsafeWindow.Tumblr.KeyCommands;
        if (e.altKey && code == 9) {
          ctx.blog_switcher({
            toggle: 'start',
            shift: e.shiftKey
          });
          return false
        }
        if (e.altKey && code == 192) {
          ctx.blog_switcher({
            toggle: 'start',
            shift: true
          });
          return false
        }
        if (e.altKey && code == 27 && ctx.tab_switching) {
          ctx.blog_switcher({
            toggle: 'cancel'
          });
          return false
        }
        if (e.altKey && code == 37 && ctx.tab_switching) {
          ctx.blog_switcher({
            toggle: 'start',
            shift: true
          });
          return false
        }
        if (e.altKey && code == 39 && ctx.tab_switching) {
          ctx.blog_switcher({
            toggle: 'start'
          });
          return false
        }
        if (e.altKey && code == 82 && ctx.logged_in) {
          for (i in ctx.post_positions) {
            ctx.fast_reblog(i, ctx.post_positions[i])
          }
          return false
        }
        if (e.altKey && code == 69 && ctx.logged_in) {
          for (i in ctx.post_positions) {
            ctx.fast_reblog(i, ctx.post_positions[i], true)
          }
          return false
        }
      }

    },
    'keyup': function (e) {
      var code = e.charCode ? e.charCode : e.keyCode,
        modified = (e.shiftKey || e.ctrlKey || e.altKey || e.metaKey);
      if (navigator.platform.startsWith("Linux")) {
        var ctx = unsafeWindow.Tumblr.KeyCommands;
        if (!e.altKey && ctx.tab_switching) {
          ctx.blog_switcher({
            toggle: 'stop'
          });
          return false
        }
      }
    }
  });
})(unsafeWindow.jQuery);

unsafeWindow.jQuery(document).ready(function ($) {
  new KeyCommandsForLinux();
});