As others already mentioned, you can`t list channel users via Bot API.
But you can use MTProto AP
I to login as a plain user and have programmatic access to everything you can see in desktop or mobile application.
To use MTProto, you need to login to https://my.telegram.org/
with your existing Telegram account and get credentials:
api_id and api_hash. https://stackoverflow.com/questions/33844290/how-to-get-telegram-channel-users-list-with-telegram-bot-api#33856213 https://docs.madelineproto.xyz/