Single user
<a href=”https://teams.microsoft.com/l/chat/0/0?users=user@domain.tld”>Chat with User</a>
Multitple users
<a href=”https://teams.microsoft.com/l/chat/0/0?users=userA@domain.tld,userB@domain.tld”>Chat with Group</a>
With Topic and Message
<a href=”https://teams.microsoft.com/l/chat/0/0?users=userA@domain.tld,userB@domain.tld&topicName=This is the topic&message=This is the message”>Order more</a>