(In reply to comment #0)

When JavaScript is disabled you get at the moment a useless button because the
button is inserted in the HTML but the functionality is only in JavaScript.

Either the button gets hidden without JavaScript e. g. by creating the button
with JavaScript, or the functionality get available without JavaScript e. g. by
creating a special page [[Special:Universal Language Selector]] which allow
changing the language by a single click. This would also solve Bug 41988.

ULS requires JavaScript. In this day and age, more advanced functionality is only available when enabling JavaScript in more recent browsers.

There is easier way:

.client-nojs .ulsSomething { display: none; }

OR

// Make it hidden by default and
.client-js .ulsSomething { display: foo; }

Having dummy icon that does nothing is different issue from the issue of making ULS work without JS.

REOPENED: Hiding the useless button with CSS is also a solution.

*** This bug has been marked as a duplicate of bug 42500 ***