The fun thing about this is when I look on my install of gitlab install for
apt-cache policy ruby-rails
dpkg also tells me I do not have ruby-rails installed.
Witch to me would indicate that similarly to how they bundle nginx with their omnibus install they do not actually use the ruby from your repos, but a bundled version that’s exactly what they need instead from their own repos.
So I’m not very convinced anymore that instlaling packages would fix that without trying it on a pi myself.
But things may be different on the arm builds. Since it tells you to look for that version try and find if you can install it anyways.
Community docker images would be an option, but the official one does not seem to support arm either.