@mpeterson0418 I found that the root file system was either corrupt or "reset" . I don't know and unable to guess what happened to the disk (maybe power outage?), but I can explain what I did to recover.
I found host MySQL to be empty. The box database had tables but was empty. The fact that it had tables meant that migration scripts were run on this . Maybe /home/yellowtent/box/setup/start.sh was run at some point on an empty (i.e no tables even) database.
Usually, the last well known mysql dump is located /home/yellowtent/boxdata/box/box.mysqldump . One can also find the same inside the latest backup (inside the box.tar.gz) .
To "restore", mysql -uroot -ppassword < /home/yellowtent/boxdata/box/box.mysqldump
Then I found, docker won't start. In Cloudron, containers are throw away infrastructure since data is stored outside the containers. I tried cloudron-support --recreate-docker but this did not work. On investigating further, it seems /var/lib/containerd was also corrupt . Corrupt here means no docker commands work. So, I removed that directory as well. After that, cloudron-support --recreate-docker worked.
The best way to migrate in Cloudron is not to do the above but instead just restore from backups. See https://docs.cloudron.io/backups/#move-cloudron-to-another-server .