You might want to prevent everyone in a meeting from being able to present, perhaps you work in Education or something. You can only do that via Powershell at the moment, because Microsoft.
Install SfB Online Powershell Module https://www.microsoft.com/en-us/download/details.aspx?id=39366
$sfbSession = New-CsOnlineSession
or if, like me, you’re in a hybrid set up and your account is homed On-Premise you’ll need to do
$sfbSession = New-CsOnlineSession -OverrideAdminDomain "yourdomain.onmicrosoft.com"
Once connected you can see your meeting policies and the current DesignatedPresenterRoleMode with
Get-CsTeamsMeetingPolicy | ft Identity, DesignatedPresenterRoleMode
Set your policy to allow only the organiser to present by default and allow the presenter to override this setting. I’m going to do this globally but obviously replace the identifier with whatever policy name you want to set.
Set-CsTeamsMeetingPolicy -Identity Global -DesignatedPresenterRoleMode OrganizerOnlyUserOverride
You can set four options here, which are self explanatory