Pathing will vary based of which QBs you have installed.
"C:\ProgramData\Intuit\QuickBooks 20XX\Components\QBUpdate\Qbchan.dat"
An Example:
Line 4 (Value needs to be change to BackgroundEnabled=0 from 1)
The update option will stay toggled off, unless you accidently click "Options" tab for updates. I highly suggest you create a scheduled task that runs twice or however many times you want. And yes this allows for users to do manual updates still.
[ChannelInfo]
NumChannels=47
NotifyClass=QIHndlr.Handler
BackgroundEnabled=0