The server log says "PROXIED attributeDescription "MEMBEROF"
inserted"; if I specify the attribute explicitly (e.g. ldapsearch
uid=liam memberof) the memberOf attributes are displayed, but all
in capitals, as if there's a schema missing.
The schema definition of memberOf is in fact missing in the proxy.
That definition is hardcoded in slapo-memberof(5). Your build
probably has slapo-memberof(5) built as module, or not built at all.
You need to just load the module, so the schema definition takes
place.