Cannot install Gitlab on RPi3 armv7l GNU/Linux

I followed the steps on this page (I tried both Debian and RPi2) to install Gitlab on my Raspberry Pi 3rd gen (armv7l).

Everything works until step 2.2 (installing the gitlab package; adding the gitlab package repo was successful).

E: Unable to locate package gitlab-ce or
E: Unable to locate package gitlab-ee

The /etc/apt/sources.list.d/gitlab_gitlab-ee.list was successfully created:

deb stretch main deb-src stretch main

And I updated via apt-get.

In addition, apt-cache search gitlab-ee (or -ce) does not return anything.

Any help is appreciated.

Unfortunately, I just found out that Debian Stretch is not supported yet. Bad news, but this issue can be closed then.