Greasy Fork is available in English.
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-late'25 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This script was originally made by xX_LegendCraftd_Xx (this was before he deleted his script after he archived it), but I re-added this script myself but with fewer tweaks applied to this.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.