If the hostname is the IP of the server, then you cannot transfer without your users noticing it, because the server IP is in the key they use. Unless you somehow transfer the IP addresses as well, which is sometimes possible if your move is inside the same VPS provider. If so, then you can take a snapshot of each VPS and move it wherever you want.
vdsina.
I don’t think the best solution would be to take a snapshot of the entire server. It seems to me that somehow it is possible to transfer docker.