It seems the new proxyAuth feature has to be configured in the setup of custom manifest add-on. Why can this not be added to the settings page of an App Proxy so it can be configured on the fly?
That's right. I had expected in 7.4.0 to be able to open settings for an App Proxy and tick a box (or similar) enabling authentication. But glad to know it's on the road map somewhere.
Ah this was my fault, I didn't approve the required app package version. This done now. So if you setup a new proxy app via your Cloudron dashboard, the user-management options should be available now.