[keycloak-user] Keycloak as ID provider for large amount of devices

Hello We are planning to get a lot of devices, identifyable by individual certificates, into an IOT-system being designed and developed at the moment. We choosed to authenticate all actors (users, software components and devices as well) by OIDC-tokens and (pre)decided to use Keycloak as ID provider. User and software components are quite straightforward to handle with Keycloak (as Keycloak users with the help of a user federation provider & id brokerage and for applications as Keycloak clients respectively). But I am not sure of how to represent our devices (we want to support hundreds of thousands of them later on!) by Keycloak means. It seems that we essentially have 2 possiblities to register a device in Keycloak - As a user - As a client By representing devices as Keycloak clients we might take advantage of the ServiceAccount (Oauth-Client Credential) flow and become able to implement it via (dynamic!) registration and it and seems, that we will even be able to authenticate our device by their certificates by choosing "Signed Jwt" as authenticator option. My question is, if it would be a good idea to register a very big amount of devices as Keycloak clients with regards to performance and manageability. In principle I would prefer a user-representation (faciliting usage of user federation provider & id brokerage for instance), but as far as I understood, the appropriate flow would be Direct Access (ResourceOwnerPassword Credentials) and here we can only deal with username/password instead of certificates. Do you have any suggestions or hints (even the conclusion, that Keycloak is not the suitable ID-provider-implementation for large-scale IOT-systems)? Best regards, Eduard Matuszak