The M8 does support disabling updates if the System Update app is recent. Here is how to check on the device:

*Go to Android settings > Apps&Notifications -> SEE ALL APPS
*Select the vertical ellipsis in the upper right part of the screen and select “Show system"
*Then check SW version of “System Update”, if the version is newer than V8.1.3.191127, then the M8 will support disabling updates.