I recently decided to switch my Auth for cloud services over to Indieweb. It has huge benefits on platforms hosting user generated code as the user identities are transferable out of the box and don't require pre-approved redirect URIs. Hence, it works very well for authors on observablehq.com who move code around user content domains.

https://observablehq.com/@endpointservices/auth

I use this Auth as replacement for Firebase Auth... I can issues tokens for backend services using Indieweb identities that engage with Firebase security rules.

Anyway, I am super excited to have observable/Firebase/Indieweb all interoperable