This feature is available in our paid editions. Contact us here, and we'll be delighted to assist you!
If you would like your users to use your own OAuth2 apps, we recommend you check this.
If you would like to only show specific hubs to your embedding users, we recommend you do the following:
1

Tag Hub

Tag the hubs you would like to show to your user by going to Platform Admin -> Setup -> Hub, selecting the hubs you would like to tag and hit Apply TagsBulk Tag
2

Add Tags to Provision Token

You need to specify the tags of hubs in the token, check how to generate token in provisioning users.You should specify the hubs claim like this:
{
    /// Other claims
    "hubsFilterType": "ALLOWED",
    "hubsTags": [ "free" ]
}
Each time the token is used by the embedding SDK, it will sync all hubs with these tags to the token’s project. The project will only contain the hubs that contain these tags.