I'm new to Blue Ocean, and I'm following the tutorial which tells me to run:

docker run \
--rm \
-u root \
-p 8080:8080 \
-v jenkins-data:/var/jenkins_home \
-v /var/run/docker.sock:/var/run/docker.sock \
-v "$HOME":/home \
jenkinsci/blueocean

It fired up the docker instance, I got to the Blue Ocean screen, Clicked on create a new pipeline, set the GitHub token, Etc.

Update: this also happens when running Jenkins from java directly on my laptop, and installing Ocean Blue plugin:

java -jar jenkins.war --httpPort=8080

Now I'm at the part where you select the Agent, but mine has no agent:

Moreover, if I click the save button and then "save & run" it gets stuck and the docker container output throws:

WARNING: Error while serving http://localhost:8080/blue/rest/pipeline-metadata/agentMetadata
java.lang.reflect.InvocationTargetException
... <stack trace here> ...

Caused by: java.lang.NoSuchMethodError: org.jenkinsci.plugins.pipeline.modeldefinition.agent.DeclarativeAgentDescriptor.all()Lhudson/ExtensionList;

 
I posted this problem on Stack Overflow but somebody said this might be a new bug. Hope this report helps.