Here is what I have done so far:

• I update the app and changed the appid and callback urls and installed it on the emulator. Tried to do SSO again but it still doesn't work.
• I updated the AppAuth lib to the latest version, but still doesn't work
• Changed a few settings in Keycloak to make sure the cookies are persistent (like enable "Remember Me", override the SSO timeout values etc), I can see in the browser that the cookies are persistent, but still SSO doesn't work on iOS
• To make sure it is not a problem with SFAuthenticationSession itself, I tried this example: https://github.com/dvdhpkns/SFAuthenticationSession-example. I built 2 apps with different ids and run them both on a device. Then I login on the system browser to create a cookie, and I can confirm that I did get the cookie value from both apps. So that means it is possible to share cookies between the system browser and SFAuthenticationSession.

So at this point I think we are hitting a blocker. I have sent an email to the Keycloak-user ML and see if I can get any help.