I've a requirement to setup customer community(SSO based Authentication/ No Username-Password login allowed) with few Pages to be displayed if User is coming to community for the first time.
Here, we have two kind of Users, one which are completely new to system and don't have any User already created for them in database. Another, which are already in database because these users use different communities under same Org.
For non-existent(no user in database/not part of any other community) users, I am using Login Flow to check if User is coming for the first time using boolean flags in User record and show pages.
For already existing users(use other communities), I was planning to use permission set to give access to my community and use CustomLandingController to land them on form pages by checking their boolean flags.
Since, login flows can be used only with profiles and one profile can have only one login flow associated, I cannot associate login flow for existing user's profile. I cannot modify profile settings for existing users because same profile is used by other communities and have their own login flows in place.
Whole scenario works fine for non-existent(no user in database/not part of any other community) users but for existing users(use other communities), CustomLandingController doesn't seem to be working. It is not executed upon login.
If CustomLandingController does not work with SSO, then Can anyone suggest me a workaround for this or what should be my approach for existing users?