Curl (35) trying to install Gitlab Ubuntu server 18.04
Solution 1:
Usually when you have certificate errors like this you should always make sure you are accessing the correct websites and you are not redirected somewhere else.. but in your case I do not think it's the case.
In order to fix this do:
apt-get clean && apt-get update && apt-get upgrade
This should clean your repos cache and update everything. You have an old version of curl and OpenSSL and this issue I think is OpenSSL related.
Upgrade everything and it should work.
If not, to bypass ssl checks use:
curl --insecure https://packages.gitlab.com/install/repositories/gitlab/gitlab-ee/script.deb.sh