Ok, so moving to another Mastodon server *is* easy, but list migration still isn't. If you follow more than a hundred or so accounts, sorting your follows into separate feeds via Lists is super helpful. You can export your lists, but there's no import process and rebuilding them manually is painful. As usual though, there's a community tool for every Mastodon problem. My lists are back in order thanks to @Eliot_L's masto-list-importer: https://www.eliotlash.com/masto-list-importer/