So, I had set up a solr core modelled on the 'multicore' example in 4.10.3, which has no /browse.
Upon request, I went to set up /browse. I copied in a minimal version. When I go there, I just get some XML back: <response> <lst name="responseHeader"> <int name="status">0</int> <int name="QTime">4</int> <lst name="params"/> </lst> <result name="response" numFound="0" start="0" maxScore="0.0"/> </response> What else does /browse depend upon?
