I suspect the plugin has mostly been tested using hpi:run, so currently when deployed somewhere, the main link of the /blue page will lead to a 404.

I think the problem is that /jenkins is prefixed here: https://github.com/batmat/blueocean-plugin/blob/f507cd9ccd98c594719dc4dd4ae32aa94ff3fa51/blueocean-dashboard/src/main/js/components/Pipelines.jsx#L41 when it should use Jenkins.getRootUrl() for the beginning of the PATH.

E.g. the issue is visible when running the demo Docker image: docker run -p 8080:8080 jenkinsci/blueocean

I've set the priority to Important since this is the main link of that page that's not working.