$ sudo apt-get update
$ sudo apt-get install deja-dup-backend-s3 

deja-dup-backend-s3 is installed in your system.

Make ensure the deja-dup-backend-s3 package were installed using the commands given below,

$ sudo dpkg-query -l | grep deja-dup-backend-s3 *

You will get with deja-dup-backend-s3 package name, version, architecture and description in a table

deja-dup-backend-s3 package basic information: