Recently I've been exploring the FedCM API, looking at implementations for IBM Security Verify Access in both the roles of Identity Provider and Relying Party. I've put together a couple of different README's and some associated assets in case you want to try this out for yourself. I'd suggest starting off with the Relying Party implementation first, before considering the Identity Provider. Find all the assets in my blog assets repository here:
https://github.com/sbweeden/blog_assets/tree/master/fedcm