tlauen sorry, as I have already pointed out at Discuss, this is just not possible. FreeFlarum does not support migration into FreeFlarum (outbound migrations are perfectly fine), nor converts foreign database dumps to Flarum’s format. FreeFlarum is meant for new and small communities, and its infrastructure does not support incoming and existing, grown forums.
The only services that specialise solely in Flarum hosting and that I am aware of are FreeFlarum and Blomstra - otherwise, you can rent a cheap (preferably VPS) server and install & convert the database files yourself, or hire someone to do it for you.
I’d recommend you to ask at https://discuss.flarum.org, or post in existing discussions on that forum, as FreeFlarum is not affiliated with the Flarum project and this is just not the purpose of the service.
