OpenID Providers are implementations based on Open ID Connect, like servers or services or libraries. Open ID Providers are listed on the official Open ID Connect page: https://openid.net/developers/certified. Popular services like Google, Microsoft, or Amazon support Open ID, but each Open ID Provider can define different metadata describing the Open ID Connect configuration. Therefore not all Open ID Providers are supported with Picturepark.
If you plan to enable federated authentication for your Picturepark you may check support for your preferred Identity Provider with Picturepark first.