I too would like to see SAML/SSO supported in these apps. Maybe if they update them to Experience Builder?
Our workaround for this was to host our own copy of the apps at our University. This allowed us to make the small modification necessary to reference our ArcGIS Online organization, so that users are directed to its login experience, which includes includes our SAML/SSO login option.
You can download the whole repository of Imagery-Apps from github, or just the app you need. Next, deploy it on your own web server, and then create an Application item in your ArcGIS Online organization to point to your copy of the app, and generate an appId for it.
Once you have your appId, make a small change in the app's config.json: update the value for portalURL to point to your organization, and value of appId to the one for your copy of the app:
...
"portalUrl": "https://<your_org>.maps.arcgis.com",
"appId": "<your_appId>",
...
If you are deploying more than one of the Imagery-Apps, then you would generate a separate appId for each, and edit their individual config.json files accordingly.
Hope that helps!
