Please check “Teams/Skype Consumer chat and calling interop” on the public roadmap at microsoft.com/microsoft-365/roadmap?filters.. for updates.
Adding any emoji as a reaction remains under review.
I am marking this as partially done to let you know a new reactions bar with Like, Heart, Laugh, Surprised, Sad, and Angry has begun rolling out to all users.
This feature remains on the backlog. We will update you when we have status changes to share.