It is a misnomer that it is sufficient just to change the url. My userscript that will check and if necessary, either change or add the required cookie preferences in addition to the URL swap. I wrote it so that if no change is needed, it literally does nothing and simply passes through. Also, as opposed to all the other scripts I have seen, mine not only will ONLY change the couple required (current) preferences in the cookie, but also performs substantially better than the couple others I have seen that even come close to accomplishing all the required changes as the others were written FAR too unnecessarily complicated.
Also, if YT suddenly adds three new cookie prefs (while they even still allow the "old" site design), I've written this in such a way that it is literally a single line of code for me to update.
Below is the GH source URL, which I will always update first. Even if you install here at GF, note I use the source as the update URL, so once installed it should be checking GH, anyway. I also chose a very easy to remember URL if you choose to later install on other systems - it is github's .io SLASH initials for Y-outube O-ld S-ite D-esign. :)
07-18-2018: v1.0.1 - URL change is no longer needed 08-17-2018: v1.0.4 - Re-added new code to properly fix the 08-16-2018 layout issue (thanks to reddit user pop1040 for posting the code)