I had the same problem.
I referred to joshrhyked's post, and I succeed burn with the following steps.

1. Start Terminal App.

2. Install homebrew.
   Please refer to the installation on the page.
   https://brew.sh/

3. Install python3
   Please type the command.
   $ brew install python3

4. Put a symbolic link
   $ sudo ln -s /usr/local/bin/python3 /usr/local/bin/python

5. Start M5Burner on Terminal
   $ /Applications/M5Burner.app/Contents/MacOS/electron-m5burner-v2-eletron

best of luck to you!