What is the
≠ sign Alt code to type in a plain text editor, for example a
textarea? I've already tried Alt+2260 to no avail. Is it possible without touching the Registry settings?
Is it possible without touching the registry settings?
The ≠ sign does not have a codepoint in Windows Western codepage. It is a strictly Unicode character. Therefore, If you do not want to edit the Registry to enable the obvious solution, frankly, you have very few choices left.
The Alt+8800 key combination generates your desired result in Microsoft Word 2010 (or later) or in Character Map (when an appropriate font is selected). You can then copy and paste the result. (The earlier editions of your question implies you have tried this combination in other places before.)
The other solution is to use AutoHotkey, by writing a script to do your bidding. That, of course, entails you learning it.
Another solution is using Microsoft Keyboard Layout Creator to create a keyboard layout that has ≠ on it. It is compatible with Windows 2000, Windows XP, Windows Server 2003, Windows Vista, or Windows 7. So, if you have Windows 8, 8.1 or 10, you must depend on your luck.