Universal Containers (UC) has an existing Salesforce org configured for SP-Initiated SAML SSO with their...

The Entity ID is a unique identifier for a service provider or an identity provider in SAML SSO. It is used to differentiate between different service providers or identity providersthat may share the same issuer orlogin URL. In Salesforce, the Entity ID is automatically generated based on the organization ID and can be viewed in the Single Sign-On Settings page1. If youhave a custom domain set up, you can use https:// [customDomain].my.salesforce.comas the Entity ID2. If you want to use the same IdP for two Salesforce orgs, you need to use different Entity IDs for each org, otherwise the IdP will not be able to distinguish them and may send incorrect assertions. You can also use different cer tificates, issuers, or login URLs for each org, but usingdifferent Entity IDs is the simplest and recommended way3.