Answer by Halfgaar for Configure OpenLDAP with TLS=required

I seemed to have gotten it:

I did this:

dn: olcDatabase={1}hdb,cn=configchangetype:  modifyadd: olcSecurityolcSecurity: tls=1

And that seems to have the desired effect. I can still run commands like:

ldapsearch -LLL -Y EXTERNAL -H ldapi:/// -b cn=config

But trying to bind with "ldapsearch -xLLL -b ..." without SSL says: "TLS confidentiality required"