Hello @wendel99, I was able to reproduce your issue with a Fresh Debian install. Interestingly, it required a third fresh installation for me to encounter it. While the problem doesn't always arise, it did in your case.
I believe I've found a solution for the problem. It appears to have been caused by a race condition, which occurred when checking if config.php was writable. This was done by writing a test to the file and then removing it. Occasionally, this could cause a problem when the database and config credentials were being written in the subsequent step.
You can check out the fix here:
https://github.com/itflow-org/itflow/commit/bd9b5bdc2ff6a2c44ba16f68901ec955295467b8
Please give it a try by installing a fresh copy of Debian 12 and running the script.