This bot logs all messages sent in every channel it is in, and sends them to a log channel. You will have to specify the channel to send it to, and use your own bot token/ID.
The message format for the log is "[Username]: [Message]" There is a second version which has the format "#[Channel]: [Username]: [Message]" which can be set up the same way.
If channels are being spammed extremely fast it will start to become behind on messages. Don't worry, it will catch up eventually.
To set up the bot, take the channel ID of the channel you want the bot to send the messages to, and replace "LoggingChannel" with it.
Take the bot's token, and replace "BotToken" with it.
LightningBoy2527/Loggin-Discord-Bot
This bot logs all messages sent in a channel it is in, and sends them to a log channel. You will have to specify the channel to send it to, and use your own bot token/ID.
Python