It's kinda weird that nobody has posted this information anywhere on the Internet because there actually IS a way to disable Windows Update completely. Why would you do that? While keeping your PC up to date is recommended, some people experience huge issues with updates. Windows Update has broken various PCs I have worked on (home PCs/laptops, PCs at work, work servers, etc.) numerous times. This is why I prefer to update Windows only when I do have the time to also reinstall Windows in case it breaks something I really need (which is almost always). I dislike forced updates that I have no controls over because they break shit way too often.
So, how is it done? Windows Update depends on 2 services on your PC to function. If you simply delete these two services, Windows Update will stop. Why both? Because these services attempt to restore each other, hence both must be removed.
1. Press Windows+R.
2. Type in "regedit" and press ENTER.
3. Find and delete the entire the key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wuauserv
4. Find and delete the entire the key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WaaSMedicSvc
5. Restart your PC.
6. Make SURE you actually DO restart your PC! The services will be running even though you deleted them from registry until you restart your PC. That means that they have a chance to restore each other. For extra safety you can first stop those 2 services before deleting them. While technically you may not need to restart your PC if you go this route, safe is safe and you should restart it anyway.
Optional: Export the two keys from the registry so you can restore Windows Update if necessary.
Notes: There are other ways to delete services via command line, but even in admin mode, Windows will actually refuse to delete WaaSMedicSvc because of permission limitations. Microsoft is trying really hard to keep pushing those (essentially beta) updates on you.