Broken SSO authentication with the new update

[caggles]

• Your Rocket.Chat app version: 4.1.0
• Your Rocket.Chat server version: 1.3.2
• Device (or Simulator) you're running with: various iPhones (between 7 and X) running iOS versions 12.4.1 and higher

Since the new update, some of our users have been complaining of being unable to login to our rocketchat server on iOS. They are capable of getting in on PC and through Safari on their phones, but the app produces the following error:

Error loading page

Domain: NSURLErrorDomain
Error Code: -1200
Description: An SSL error has occurred and secure connection to the server cannot be made.

We authenticate to our private rocketchat server using Keycloak SSO with two providers: GitHub, and our internal enterprise user accounts, which communicates with Keycloak using SiteMinder. GitHub works fine, but if they're using their internal user account, we get the error above. It worked fine before the update to app version 4.1.0.

Has anyone else had a problem like this?

[caggles]

Further investigation has found that our SiteMinder logon page doesn't have PFS turned on. Would this be sufficient to cause this error? Does the RocketChat iOS app require PFS?