Open REGEDIT go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\edgeupdate
copy the Imagepath open a cmd window as admin and run this
netsh advfirewall firewall add rule name="Disable Edge Updates" dir=out action=block program="C:\Program Files (x86)\Microsoft\EdgeUpdate\MicrosoftEdgeUpdate.exe" <<< should match the path in regedit now Edge cant update
You can verify this inside Edge going to the "edge://settings/help" page and it will show updates are being firewall blocked. You can find these steps on winaero.com's site in more detail or google its a simple firewall rule just done by hand.