Class JDispatcher not found (Joomla 4)

Error

In Joomla 4 this PHP error appears:

Class 'JDispatcher' not found

Probable cause

If you are Smart Slider user for many years now and you used Smart Slider 2 too, it is possible that on your website you still have its files, which can create this error message. This is the list of folders created by Smart Slider 2, which should be deleted:

\administrator\components\com_smartslider2\
\components\com_smartslider2\
\libraries\nextend\
\modules\mod_smartslider2\
\plugins\nextendslider[*]\
\plugins\system\nextendlibrary\

Default cache folder:
\media\nextend\