Show fallback on authentication coordinator

RiotSwiftUI/Modules/Authentication/Common/Service/MatrixSDK/AuthenticationService.swift

@@ -138,9 +138,7 @@ class AuthenticationService: NSObject {
         loginWizard = nil
         registrationWizard = nil
         
-        // The previously used homeserver is re-used as `startFlow` will be called again a replace it anyway.
-        let address = state.homeserver.addressFromUser ?? state.homeserver.address
-        self.state = AuthenticationState(flow: .login, homeserverAddress: address)
+        self.state = AuthenticationState(flow: .login, homeserverAddress: state.homeserver.address)
     }
     
     /// Continues an SSO flow when completion comes via a deep link.

RiotSwiftUI/Modules/Authentication/Common/Service/MatrixSDK/AuthenticationState.swift

@@ -66,5 +66,24 @@ struct AuthenticationState {
                                              showRegistrationForm: registrationFlow != nil,
                                              ssoIdentityProviders: preferredLoginMode.ssoIdentityProviders ?? [])
         }
+
+        /// Needs authentication fallback for login or registration
+        var needsFallback: Bool {
+            switch preferredLoginMode {
+            case .unsupported:
+                return true
+            default:
+                break
+            }
+            guard let flow = registrationFlow else {
+                return false
+            }
+            switch flow {
+            case .flowResponse(let result):
+                return result.needsFallback
+            default:
+                return false
+            }
+        }
     }
 }