Ask HN: How do online marketplace platforms acquire an initial user-base?

Hi HN. I am developing an online platform, where users can find other users to perform a specific service for them; similar to Fiverr but a lot more niche. These types of platform can only work if there is a healthy portion of users that provide services and a decent portion of users who want those services. As such, how do you launch such a platform with zero/little users? You could acquire the service providers prior to launching (e.g.: via a pre-lease sign up page and a marketing campaign to go alongside) but that has its own issues: for starters, no-one will have any reviews, and from a technical perspective you'd have to implement a way for those users to complete their profiles before launch. I have seen suggestions of faking a user base, but that does not sound appealing to me and I am not sure of its legality.