I am currently working on using OpenID Connect with Matrix Synapse server. We are planning to have a centralized OpenID Connect provider for all the apps. In a few days, I will update you on how its going.
In the last group meeting, we discussed Element Calls as a way for getting multi-participant audio/video calls. We don’t have an implementation plan for it yet but we certainly will do our best to ensure A/V calls are working well in Matrix.
Yes, FreedomBox apps will be able to use OIDC provider for authentication. Current plan is to implement OpenID Connect provider within FreedomBox web interface. If deemed better, it will be separate daemon running within each FreedomBox, not an external server.