Open WhatsApp on your device and navigate to the "Chats" tab.
Select the specific WhatsApp group to which you'd like to add unknown contacts.
Within the group chat, locate and tap on the three-dots menu icon situated at the top-right corner of the screen.
A dropdown menu will appear; from this menu, select "Group info."
Scroll down the "Group Info" screen until you find the option labeled "Invite via link" and tap on it.
After tapping, you'll get the WhatsApp Group Invite Link and a message stating that anyone with WhatsApp can join the group via this link.
Below the message, tap "Share link." Then choose your preferred method to share, like through Gmail, SMS, or other messaging apps.