Hi,
In the docs, 1. Basics, “requirements”, “composer” is not mentioned.
Never-the-less, (on Ubuntu) “composer” is a separate package that you need to install with the Ubuntu package manager, in order to utilize this methode.
You might want to list it as an (optional) requirement, since some newbies will not have any knowledge of the composer.
Just my $0.02
Hi Peter,
when installed via download, Grav ships its own copy of composer which handles all the stuff inside itself.
So composer is only required to have before when using composer install method, which is surely not something that basic users would do, isn’t it?
He Chris,
Call me “not basic”, but it was my preferred method 
Cheers,
Peter
The GitHub repository does specify installing through Composer, but Composer itself is not a dependency for installing, running or upgrading Grav. This can all be done through archives published as releases or pre-built packages.