You can generate a beautiful m.me link for your Messenger channel by creating a username for your Facebook page
Facebook will use the Facebook page username to create your 'm.me' link. Without one, it will generate a string of random numbers. Resulting in m.me/123456789, for instance.
To create a pretty m.me link, you have to create a username for your Facebook page.
On Facebook.com navigate to your Facebook page and click the ‘about’ section in the sidebar on the left. There, you’ll see ‘Create Page @username’ at the general section.
Click on it and you’ll be prompted to create a username. After you’ve created your new username you can access your bot on: m.me/[username].