Marketplace with additional implementations

hi we want to develop a service marketplace to allow consultants to have consultaions with clients. We were looking at sharetribe flex as it had 80 percent of what we need and we thought we could build on it with custom react and js components but a develiper on upwork said with flex you can only develop the ui?

He said to use community edition is this right?

Does anyone know of a solution like flex that will allow custom development on top?

Thanks