After the database had restored, postgres_data was 24G.
Something in the migration had postgres_data balloon to 91G before the disk filled and the restore failed. This is on a clean install with the Discourse versions shown above.
This seems like it must be a bug, so I’m recategorizing. I’ve also seen it when trying to upgrade. I’d thought for that upgrade that a solution would be to move to a new server, but now I see that won’t work.
I guess the next thing to do will be to try to see what query is causing this and/or what table it is. I’m not quite sure how to go about that.