Joomla! 4 introduced the new left sidebar which unfortunately, looks quite unusable and frustrating for some users.
Since Google started to use Cumulative Layout Shift (CLS) metric in PageSpeed Insights, most of websites with YOOtheme Pro template were affected and the mobile page score is much lower than before.
Enjoy Joomla 4 debug for Joomla 3: https://github.com/AlterBrains/joomla3debug4
By default, Joomla core and other 3rd-party extensions loads bundled jQuery from JUI: