Do we receive a message in teams, an email or a phone call? Before being laid off?.

First would be a formal email for face to face with RMG or HR. In some cases HR might reach out to you in Teams or Google Chat to have a face 2 face. They will be informing you directly. Incase you are WFH then it would be done through a meet followed up by an email.
They may give options as well.

RMG one to one interview

What did you receive?

You will get a mail and/or call from HR or RMG, depending on the scenario your case is in.