I have followed the instructions in https://wiki.gnupg.org/LDAPKeyserver to
configure our LDAP server to act as a keyserver. This works fine with GnuPG 1
and 2.0 but not with 2.1.

From the testing I've carried out, it does not seem possible to upload keys to
LDAP anonymously, but I cannot find any documentation for GnuPG 2.1 that
explains how to specify a username and password for use with an LDAP keyserver.

I've tried various options in the dirmngr configuration with the keyserver
configuration but none of them work, so I'm not sure if this works or if it is
a lack of documentation.