Actually, I use my iPhone with a USB-C/HDMI cable, the Remote Desktop client and a Bluetooth keyboard when traveling. Some apps will let you use an additional display just fine.

Oh interesting, I suppose I have had it wirelessly project to the tv before...

I might give it a go when I upgrade to a USB-C model.

OK so I've now tried this with a new USB-C iphone.

Yeah it's painful to use! You can set up a mouse, and use a physical keyboard for input, but it doesn't attempt to do any more than mirror the screen onto the external device by default.

Huawei's desktop mode was limited, but I think you're right - you can say the iphone has good device compatibility, but there's not a good way to use it docked. Not that the android ones were 'good', but they made an attempt!

Great, can I plug a USB drive in, and use it?

Which is quite frankly weird, given that the iPad has fairly robust mouse/keyboard support at this point, and at least some nods towards window management