The easiest way to get the latest stable release is from snap:
snap install deja-dup --classic
You can also download a source tarball and compile it yourself.
To install the latest version in development, you can also use snap. Please don't rely on development releases for your actual backups though!
snap install deja-dup --classic --edge
git clone https://gitlab.gnome.org/World/deja-dup.git