"I imagine it must be a bit frustrating with other providers, though."
And you wonder why - it's a matter of setting user, password, and server/port.
Just, the GUI attempts to hide server settings, as if they could scare children, and if it's "synchonizing" you can't access them. Evidently, whoever wrote it doesn't know how to stop a running thread, and restart its operations. Then it uses non standard settings, like the added :n after the server port, which is barely documented. Its certificate management is appalling too - especially since it can't tell you what "problems" it has with a certificate, nor show the certificate to check it - so you can accept it blindly only.
I don't know what intern was tasked to write it, but it's a good example about how an application should not be developed. And they want to cage people into Windows S so you can only install this crap from the store?