My only concern for a native to container migration would be file permissions, as the Seafile server itself runs as root on the container (completely unnecessary, and dangerous if an attacker finds a vulnerability on the seafile server and manages to break out of the LXC) and the seafile manual instructs you to create an unprivileged user to run the server.
Other than that the migration should be pretty straight forward, just restore the database on the container and modify the directories to match that of the docker container
(Something like that, don’t use symbolic links though)