Report Builder(Beta) is available in lightning but still, most of us are using the classic version. Here, I am explaining how we can enable the lightning report builder.
Setup > Quick Find Home textbox type “report” > Select
As you can see in the above image, select the “Enable Lightning Report Builder (Beta)” checkbox and proceed with saving the changes. Now, it is enabled in your org but still, it is not available for use. Since we are lacking the permission, it is to be added to a user through profile or permission set.
Allow Permission Using Profile
Select one of the profiles.
setup > quick find box search > users > profiles > System Administrator
Edit the admin profile and select the Report Builder checkbox for lightning experience like below. The users under this profile will be able to access the report builder from reports tab.
Allow Permission Using Permission Set
Open permission sets – setup > quick find box search > users > Permission Set
Create a new permission set or edit the existing permission set for enabling the Report Builder checkbox for lightning experience under System Permissions.
Select the Report Builder for lightning experience checkbox.
Finally, you can see multiple quick actions for creating a new report.