IRIS OS Authentication on Ubuntu 20.04/22.04

I've been trying for a while now to get OS authentication working on IRIS running on Ubuntu 20.04 and subsequently 22.04. I have the following authentication methods enabled for %Service_Terminal:

• Operating System
• Password
• Operating System Delegated Authorization

And i have these options selected in Authentication/Web Session Options:

But when logging in via iris session <instancename> I am always prompted for a username and password. I am logged into the operating system with a username that matches my IRIS username, and the same configuration and login method works fine on Red Hat 8.5.

Is there something I need to do differently on Ubuntu?