I created a job of type "GitHub organization" named "inspectIT-GitHub" and added a the GitHub project "inspectIT" to it. The problem is, that I cannot use the links from the browser directly (or pressing F5), I do get a 400 back from Jenkins. If I open the links directly from blue ocean, it seems to be working fine. You can take a look at the problem in our running system:

This is the base blue ocean url: http://jenkins.inspectit.rocks/blue/pipelines
This is one of the links that is not working: http://jenkins.inspectit.rocks/blue/organizations/jenkins/inspectIT-GitHub%2FinspectIT/activity

The standard pipeline test I created works on the other hand. So it could be related to this job type.