I use a VMG8924-B10A and I can see a "TR-069 Client" option in the Maintenance menu when logged in as "admin".
It shows for me when logged in as admin also, but it didn't when I bought the device.
I added it myself via the "login privileges" menu that appears when logged in as Supervisor.
IIRC the TR-069 menu only appears in pure retail devices and not ISP unbranded devices.
My Zyxel is a former I-Talk supplied device.
If the eBay seller hadn't told me voluntarily that it was supplied by I-Talk then I would never have known.