For single sign-on, the Request Signature Method (RSM) applies a hashing algorithm—either RSA-SHA1 or RSA-SHA256—for encrypted requests. You can now apply the selected single sign-on RSM to your single logout (SLO) settings.
Where: This change applies to Lightning Experience and Salesforce Classic in all editions for Federated Authentication, and in Professional, Enterprise, Performance, Unlimited, Developer, and Database.com editions for Delegated Authentication.
How: Select Use Selected Request Signature Method for Single Logout to apply the selected Request Signature Method during SLO. If you don’t select this option, the default RSM (RSA-SHA1) is applied.
https://help.salesforce.com/s/articleView?id=release-notes.rn_auth_rsm_slo.htm&release=224&type=5