Laudspeaker offers an upsert api, where you can create users individually. You can check out the reference here ().The user schema must be set before you can use the upsert api.The main things to keep in mind is to not include system attributes in your upsert, but apart from that you can assign other attributes, including message channels like push tokens for example
Laudspeaker can ingest events via the events api. If Laudspeaker encounters a user who does not yet exist in the database, Laudspeaker will automatically create that user in the audience tab.