Allow an external participant to give or request control
Based on my knowledge, guests are able to take remote control of your screen if your organization has allowed external participants to given or request control. To check it, please sign in to Microsoft Teams admin center using an admin account and create a new meeting policy and assign it to the users or groups you want to manage. In the meeting policy, please turn on the option Allow an external participant to give or request control. For more details, here is an article for your reference: Configure desktop sharing in Microsoft Teams.
