I don't see a way to self host it. Are you willing to consider it? It seems like you're targeting a particular niche and not having it open source or self hostable seems like a mistake.
Well the primary benefit of Portabella is end-to-end encryption.
The reason for e2ee is so you don't have to trust the provider. If you're hosting stuff yourself why wouldn't you trust your own infra? As long as you've got a TLS connection to and from your servers + encryption at rest, client side encryption gives no particular benefits.
