A user, barryparr, encountered issues while updating Docker and Discourse, resulting in a non-functional installation without a backup. watchmanmonitor suggested posting logs and Docker version to diagnose the issue. After reviewing the logs, watchmanmonitor and Steven pointed out that the ./launcher rebuild command needed to be run with the correct syntax: ./launcher rebuild app. sjmscott also experienced the same issue, and codinghorror clarified the correct command. watchmanmonitor suggested improving the error message to provide the correct command. With the correct command, barryparr was able to recover their site.
The link to the log is below. I tried update Discourse, but had to update Docker first. I followed the directions on meta for updating, but had some problems.