Add note for mpremote command not found error

Added troubleshooting tip for mpremote command.

Author: richyliu

guides/fallctf-2025/badge.md

@@ -18,6 +18,8 @@ If you are on Linux, you may need to add your user to the `dialout` group to all
 sudo usermod -a -G dialout $USER
 ```
 
+If you are getting an error with `mpremote` command not found, try replace it with `python3 -m mpremote` (in all the commands below).
+
 Install the `mpremote` Python package to connect to the badge:
 ```sh
 pip install --user mpremote