FFmpeg file moving may not work on Replit's new .pythonlibs strategy. After the installation is done, run:
$ mv ffmpeg .pythonlibs/bin
$ chmod u+x .pythonlibs/bin/ffmpeg
$ ffmpeg

replit-ffmpeg

A simple tool for installing ffmpeg, libopus (opus) and youtube dl (optional) for you on Replit.

$ pip install replit-ffmpeg

To use it, simply run this in your terminal:

$ replit-ffmpeg

That's about it. Enjoy your "FFmpeg." Yup, it sounds weird.