Hello all!
Today, I publicized my script on GitHub, which store at: https://github.com/Kocoji/tel-buh-bye.
With the help of telethon, I can do the automation way to leave the group chat & channel that I have joined on Telegram, which is around 300 Group chats - in my case.
The script is short and does not have many features as the other project. But I hope this one will help you easier leave the group/channel you have joined.