Due to privacy and security policies, it is not possible and it is not ethically correct to try to access private groups on Telegram without an invitation. Private groups on Telegram are designed to be exclusive and only accessible to people with a direct invite or valid invite link.
If you want to join a private group on Telegram, the appropriate way to do so is to ask a group member to send you an invitation. You can contact a friend who is already a member, or if you know the group administrator, you can make a request directly.
If you don't know anyone in the group, private groups sometimes advertise or share their invite links on public forums, websites, or via social media to attract new members who meet certain criteria or interests. And so seeking these public invitations could be another legitimate strategy for joining the group.
Remember that trying to bypass the security layers of a platform like Telegram can violate the platform's terms of service and potentially the law, as well as be an invasion of the privacy of other group members.