Auth0 sponsors and is certified OpenID Connect provider. I personally participate in the working group and we (Auth0) help a lot on the evangelism of these standards (see: https://jwt.io and https://openidconnect.net).
let’s tell everyone to get an Auth0 account
Maybe this is not clear, but Auth0 is more close to a federation broker than an Identity Provider (we provide user/pwd storage but it’s just a feature). If you notice the implementation from the IAM team chose is passwordless (email code), LDAP or social provider, there is no password storage on any of these. This, plus the fact that all the relying parties (apps) speak the OIDC/OAuth2 standard makes Auth0 completely replaceable without having to go through bizantine migrations. This was always one of our goals: to be chosen because we provide the best platform that implements these standards. If Mozilla happens to find a better implementation, OSS or not, I would love to learn from it, and improve ours.