Using SQL Developer version 19.1 (Windows 64bit) when setting up LDAP connections the LDAP context is not being found and therefore no related DB services are returned. The LDAP context lookup previously worked in versions 17.x, was broken in version 18.2, fixed again in version 18.3, and now appears to be broken again in version 19.1.
Note this is for SQL Developer Windows 64 bit installed with the JDK 8 embedded (and therefore no separate Oracle client, network admin folder, or ldap.ora file).