Agile Filters for Jira add-on provides useful filters for JIRA Software Boards.
Without the sorting by users feature you had to create as many quick filters as assignees you have in your company.
With the Filtering on boards feature you can just set groups with assignees that you need and then select assignees from dropdown list right on board.
Go to Agile Filters Administration menu and select "Filtering on boards" tab.
Start to type group name to select one from dropdown list. Choose one or more groups to select users from them on the board later.
Then go to the board and select user in the assignee field to filter issues (the dropdown list shows first 20 matches):
Also the feature allows to search by summary field. When you enter the board all issues are opened that correspond to quick filters enabled.
Type in what you are searching for in "Summary" field and get the list of issues with the searched text in issue summary: