@lgwapnitsky No, I moved to a dedicated host for HAProxy and just about to deploy I realized it doesn't have that robust of support for directory accounts. I use Active Directory.
Also, since I asked pfSense 2.5 is came out and it's got a ton of new stuff: it now has the current (or very close to current) HAProxy, supports TLS1.3. I'll try again and come back if I'm successful, good luck to you too! :)
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PS: If you're open to alternatives for authentication, take a look at Keycloak from (backed by) Red Hat. It does federation, clustering, it provides many clients (to integrate with). OpenID Connect, OpenID, LDAPS, SAML, hardwarekeys/tokens, socials, SMS, you name it, it does it all and it doesn't even need installation, you just run the WildFly (or Tomcat/JBoss/etc..) servlet. Just charge an iPad or 'cause you'll be doing plenty or reading. It's not hard though. :)