This script forces the rounded version of the layout (which includes some fewer tweaks applied, but also includes remaining UI codes from the original RD changes, late-'23 changes and pre-delhi UI changes).
This script was originally made by xX_LegendCraftd_Xx (this was before he deleted his script after he archived it), but I re-added this script myself but with fewer tweaks applied to this.
Note: When you install this script on the non-rounded version of YouTube as a cookie setting, it will be forced into the rounded version.
