There's a bot named MDLChef in the Discord. You need to DM it, it doesn't respond in the server. On its host machine, there's a file at /opt/flag.txt - it contains the flag. Go get it.

Note: This is NOT an OSINT challenge. The source code really isn't available. Good luck.

Author: nb

Original writeup (https://github.com/glikogataki/Yet_Another_DawgCTF2021_Writeup/blob/main/MDL_Considered_Harmful.md).