Unfortunately I don’t think that new setting will help by itself - the code internals will still require passing in a secure_session object, even though it’s not used.
In general we would recommend using the official hooks for authentication plugins, rather than overriding core’s DiscourseConnect implementation.
It’s tricky to know for sure without seeing the whole plugin, but you could try passing in a nil value for secure_session. Doing that, alongside toggling the new site setting, might help get things a little closer to working.