If you are migrating from an older version of MiaB and you need to restore your mailboxes/dns/etc from a backup, the current instructions suggest that you download the backups to your client and then re-upload them to the new server.
This can be a problem if you suffer from slow upload speeds at the home or office and have several GB of data to transfer (I was getting 200 Kbps upload speeds which would have taken several hours to upload my 4GB worth of backup data).
An alternative is to create a snapshot of your old server after your final backup and then use this to spin up a temporary instance of the old server alongside your new server (preferably in the same physical location, if your provider lets you choose that). You can then directly transfer the backup archives from the temporary server to the new server, which should be much much faster than transferring the files through your home network. In my case, I used scp to download 4GB from the temporary server to the new server in less than 30 seconds.
Don’t forget to destroy the temporary instance of the old server once you’re done so you don’t get charged.
Might be worth adding this to the instructions, I definitely thought I was going to be up all night waiting on the transfer until I figured this out!