My question is: how to join my telegram bot to a telegram public channel that I am not administrator of it, and without asking the channel\'s admin to add my bot to the channel
Answer to your edited question.
It was possible to add a bot to a group/channel with just an invite link. This was achieved by allowing a bot to access the mtproto methods like messages.importChatInvite for private links and channels.joinChannel. However telegram patched this. However, you can still do this with normal user accounts! Since you are using python you can give this a shot. I can confirm the methods still work on Madeline Proto.