uBlock Origin list that Disables Youtube's Experimental UI on Desktop.
stop Youtube Experimenting on you, you are not their Lab Rat, Take back your Freedom
Use a browser that supports extensions/add-ons (I Recommend Firefox or forks of Firefox) and install uBlock Origin (Best adBlocker but it's not just an adBlocker)
Now go to uBlock Origins Settings > Filter Lists > scroll down > Import > copy and paste the link below
Fix Youtube UI
alternatively you can copy all of the filters and add them to My filters section of uBO but if you do that then you have to manually update the filters yourself
I have not made any userscripts, but there are other ones
