Migrations are not currently possible, but this is something we plan to work on.
For now, owners will need to create a new Discord/Slack and LaunchPass account, then share the new invite page with members. Existing members will need to sign up again.
Alternatively, for transitioning from Slack to Discord, you can send all existing members one-time Discord invites to get them into your group (note: if you choose this route you will need to manually kick them if they stop payment).