In SharePoint Online, by default, Microsoft has added a “Feedback” button. This may confuse end-users, as they might think the feedback will be send to their administrators instead of Microsoft.
In order to remove the button, it is sufficient to run this Powershell script on your tenant.
$userCredential = Get-Credential -UserName [admin_username] -Message "Provide your password."
Connect-SPOService -Url https://[tenantname]-admin.sharepoint.com -Credential $userCredential
Replace the [admin_username] with an e-mail address from a tenant admin, and [tenantname] with the name of your tenant.
After running the script, it might be possible that you have to wait a couple of minutes for the script to take effect.