I am not familiar with ADFS, but I have just finished setting up an integration with Azure B2C, which is likely very similar.
It looks like ADFS supports openid_connect: Migrate to the Microsoft Authentication Library (MSAL) - Microsoft identity platform | Microsoft Learn
So in theory, you can use the new discourse-openid-connect plugin. After completing the setup on the ADFS end, you just input the ‘discovery document’ URL into Discourse, along with the client id/secret. If the discovery document does not contain a “user info endpoint”, then the user information will be extracted from the JSON Web Token obtained from the “token endpoint”.
I will be adding some documentation for this new openid connect plugin this week, so please do let me know if you get it working for ADFS!