Many customers have asked how to disable "Microsoft Forms (Plan E3)" for all users via Windows PowerShell.
Claus Schiroky created a PowerShell script found here. This was originally created for Sway, but can be used for Forms.
Before running this, you may need to install the prerequisites:
Microsoft Online Services Sign-In Assistant for IT Professionals RTW
Download and install en\msoidcli_64.msi
Azure Active Directory Connection
Download and install AdministrationConfig-V18.104.22.168-GA.msi
I named this ManageServices_Forms.ps1 and placed it in C:\Temp. I then opened Windows PowerShell and browsed to that .ps1 and hit Enter.
I then chose  DISABLE a service for all users > Enter
When asked for the AccountSkuId, I chose FORMS_PLAN_E3, because my use have Office 365 Enterprise E3 licenses:
I was then asked to enter my Microsoft Office 365 global admin email address > Enter.
I was then asked to enter the Service Plan name > Enter. I entered FORMS_PLAN_E3.
Unfortunately in my test environment my FORMS_PLAN_E3 ServicePlan in still in a PendingProvisioning State. So my test does show Forms as being Disabled. But trust me, this is how you do it.
Once my tenant in no longer in a PendingProvisioning state I will update the blog.