This is the only method where This requires the group admin to be online.
2. Use the "Add Members" Feature (For Group Admins & Members) how to join telegram group without sharing link
So,
This public link is valid for 7 days and shares a thread, including any personal information you added. This link or copies made by others cannot be deleted. If you share with third parties, their policies apply. Can’t copy the link right now. Try again later. This is the only method where This requires
Publicly available links are frequently scraped by automated bots that flood groups with spam. This link or copies made by others cannot be deleted
If you are in direct contact with a group admin, they can add you manually without any link or QR code. This is the most private method because the group never generates a shareable invite.