SSO Login has disappeared from the app, both Android and iOS

[catalyst-eu]

Steps to reproduce

1. I load the app and give our company Matrix URL
2. There used to be a "login with SSO" in the app. In the browser it is still there, but the app doesn't have it.
3. As a result, I can no longer login to Matrix/Element

Outcome

What did you expect?

A button "Login with SSO".

What happened instead?

The button is not there. There's only the option to login with username and password, but that doesn't work for us.

Your phone model

Any Android phone

Operating system version

Any android OS

Application version and app store

1.4.32

Homeserver

Synapse 1.4.0

Will you send logs?

No

Are you willing to provide a PR?

No

[hughns]

I've come across what I think might be the same issue in the OIDC Playground.

Test homeserver: https://synapse-oidc.lab.element.dev

Here is how it looks on app.element.io which is what I expect:

On iOS the SSO button is missing:

And on Android it is also missing:

The issue is triggered by having https://synapse-oidc.lab.element.dev/_matrix/client/v3/login returning m.login.sso but without the identity_providers value being set.

The spec says that identity_provider is optional.

I have a patch that fixes the behaviour on Android:

I haven't found the appropriate place for iOS.