Find Activities not working in 5.19beta1 and master
It's working in 5.18.4. In 5.19+ it just always returns all activities.
It's because of a change in CRM_Core_Form_Search::setFormValues(). This now calls $this->getFormValues(), but for activity search all that does is return NULL, so no form values get set.
To upload designs, you'll need to enable LFS. More information