Fatal error: Out of memory with the Duplicator plugin

I had the same problem. And I though that this might be due to the size of my MySQL file(5GB). So I selected the advanced option for the database upload which is to upload the database manually. I didn’t succeed doing so through the phpMyAdmin interface, instead I imported it through mysql cli with :
mysql -u username -p database_name < my_file.sql

Also for more troubleshooting check the official documentation here.